<PAGE>   1

                                                                   EXHIBIT 10.42


                                 AMENDMENT NO. 9
                                     TO THE
                            GENUINE PARTNERSHIP PLAN


         This Amendment to the Genuine Partnership Plan is adopted by Genuine
Parts Company (the "Company"), effective as of the date set forth herein.

                                   WITNESSETH:

         WHEREAS, the Company maintains the Genuine Partnership Plan (the
"Plan"), as amended and restated effective January 1, 1994, and such Plan is
currently in effect; and

         WHEREAS, the Company desires to amend Schedule B of the Plan;

         WHEREAS, the Company has authorized the Committee to the Plan
("Committee") to amend Schedules to the Plan and the Committee has authorized
Frank Howard to execute such amendments without a meeting of the Committee;

         NOW, THEREFORE, BE IT RESOLVED that Schedule B is hereby deleted and a
new Schedule B is substituted in lieu thereof as follows:

                                   "SCHEDULE B

                 Credit for Service with Predecessor Employers


I.       General Rule - No Past Service. Unless otherwise identified in Part II
below, an Employee will not receive Credited Service or Years of Eligibility
Service under this Plan for any purpose. Instead (unless otherwise required by
law) Hours of Service worked for a predecessor employer prior to the Designation
Date shall be ignored.

II.      Definition of Past Service Credit. If Employees who were previously
employed by a predecessor employer are granted past service credit (as noted
below), such Employees who are employed by an Employer on the Designation Date
shall receive Credited Service and Years of Eligibility Service under this Plan
beginning with the employment commencement date with the predecessor employer,
but subject to all of the rules concerning crediting of service and Breaks in
Service set forth in this Plan.

<PAGE>   2

<TABLE>
<CAPTION>

                                                                       Extent of Credit for Services
        Name                                   Designation Date          With Predecessor Company
        ----                                   ----------------        -----------------------------

<S>     <C>                                    <C>                     <C>


1.      Odell Hardware Company                     7/1/88              Past Service Credit Granted
        ("Odell")

2.      Clark Siviter                              7/1/88              Past Service Credit Granted

3.      Brooks-Noble Parts                         7/1/88              Past Service Credit Granted
        & Machine Co., Inc.

4.      General Automotive Parts                   7/1/88              Past Service Credit Granted
        Company and its subsidiaries
        ("General Automotive")

5.      Standard Units Parts                       7/1/88              Past Service Credit Granted
        Corporation including
        its subsidiary Manco,
        Inc. ("Standard Units
        Parts")

6.      NAPA Des Moines                            7/1/88              Past Service Credit Granted
        Warehouse ("Des Moines")
</TABLE>

III.     (a)      Acquisitions Prior to January 1, 1994.

         Participants employed by the following predecessor employers that were
acquired prior to January 1, 1994, shall not receive Past Service Credit as of
the date the predecessor employer was acquired by or merged into Genuine Parts
Company. However, after an employee of such predecessor employer becomes a
Participant in the Plan by satisfying the requirements of Section 3.01, such
Participant shall receive Credited Service for all employment with such
predecessor employer effective as of the Employment Date indicated below
provided such individuals were employed by an Employer (as determined by the
Committee) on the Employment Date.

         (b)      Acquisitions On or After January 1, 1994.

         Participants employed by the following predecessor employers that were
acquired on or after January 1, 1994 shall receive Credited Service and credit
for participation purposes under Article III for all employment with such
predecessor employer effective as of the Employment Date indicated below
provided such individuals were employed by an Employer (as determined by the
Committee) on the Employment Date.

         (c)      Important Restrictions.

         Credited Service granted under (a) or (b) above may be forfeited or
disregarded in accordance with the definition of Credited Service set forth in
Article II. Furthermore, no Credited Service shall be granted for employment
with a predecessor employer if the granting of such Credited Service will
adversely impact the tax qualified status of the Plan.


                                      -2-
<PAGE>   3

         Davis & Wilmar, Inc.                         May 1, 1993
         Pittsburg, PA                                (Acquired 7/1/92)

         M&B, Inc. (Lesker Office Supplies, Inc.)     November 1, 1993
         Charlotte, NC

         The Parts, Inc.                              January 1, 1995
         Anchorage, AK                                (Acquired 1/1/94)

         Dade City Jobbing Group                      January 1, 1994
         Dade City, FL                                (Acquired 1/2/92)

         Atlantic Tracy Inc.                          November 1, 1995
         Summerville, MA

         Midcap Bearing Corporation                   June 1, 1995
         San Antonio, TX

         Motion Equipment, Inc.                       June 1, 1995
         Houston, TX

         Power Drives & Bearings, Inc.                October 1,1995
         Omaha, NB

         Friend's Motor Supply, Inc.                  June 30, 1997
         Hastings, NE

         Utah Bearing and Fabrication, Inc.           October 3,1997
         Salt Lake City, UT

         Colorado Bearing and Supply, Inc.            October 3, 1997
         Denver, CO

         Quality Auto Supply of Alaska, Inc.          April 1, 1998
         Palmer, AK

         Berry Bearing Company /Tom Steel Div.        January 1, 1998
         Lyons, IL                                    (Acquired 2/93)

         Cascade Bearings                             April 1, 1998
         Yakima, WA

         Horizon U.S.A. Data Supplies, Inc.           August 1, 1998
         Reno, NV                                     (Acquired on 4/1/95)


                                      -3-
<PAGE>   4

         Berry Bearing Company (all divisions         October 1, 1998
         other than Tom Steel Division)               (Acquired 2/93)
         Lyons, IL

         Hub Tool & Supply, Inc.                      January 1, 1999
         Wichita, KS

         Bush-Miller, Inc.                            April 1, 1999
         York, PA"

         This amendment shall be effective April 1, 1999. Except as amended
herein, the Plan shall remain in full force and effect.

         IN WITNESS WHEREOF, Genuine Parts Company, acting through the Committee
has caused this Amendment to the Plan to be executed on the date shown below but
effective as of the date indicated above.

                                        COMMITTEE TO THE
                                        GENUINE PARTNERSHIP PLAN


                                        By:   /s/ Frank M. Howard
                                           -------------------------------------
                                           Frank Howard, acting on behalf of the
                                           Committee

                                        Date:   April 5, 1999
                                             -----------------------------------



                                      -4-