<PAGE>   1
                                                                 EXHIBIT 10.16.4


                                SEVENTH AMENDMENT

                                     TO THE

                                 TRANSTAR, INC.

                            SALARIED RETIREMENT PLAN
               (As Amended and Restated Effective January 1, 1989)

         Effective January 1, 2000, the following revision is adopted by the
Transtar, Inc. Salaried Retirement Plan.

         APPENDIX A, Subsection (a) shall be amended as follows:

         (a)      Normal wages and salaries for services performed, including
                  incentive, shift differential, out-of-line differential, and
                  Sunday, holiday and overtime premium payments applicable to
                  such services, but excluding any cost-of-living payment and
                  the amount resulting from a Cost-of-Living Adjustment included
                  in the base hourly or salary rates on or after May 1, 1974
                  other than the first thirty-nine cents ($.39) per hour for
                  hourly paid employees and the first sixty-eight dollars ($68)
                  per month for salaried employees. Effective January 1, 1997,
                  Participants whose rolled into base Cost-of-Living Adjustment
                  excluded from Pensionable Earnings prior to January 1, 1997
                  exceeds six hundred dollars ($600.00) per month shall have
                  such exclusion reduced prospectively to six hundred dollars
                  ($600.00) per month. Effective January 1, 1998, Participants
                  whose rolled into base Cost-of-Living Adjustment excluded from
                  Pensionable Earnings prior to January 1, 1998 exceeds four
                  hundred fifty dollars ($450.00) per month shall have such
                  exclusion reduced prospectively to four hundred fifty dollars
                  ($450.00) per month. Effective January 1, 1999, Participants
                  whose rolled into base Cost-of-Living Adjustment excluded from
                  Pensionable Earnings prior to January 1, 1999 exceeds three
                  hundred dollars ($300.00) per month shall have such exclusion
                  reduced prospectively to three hundred dollars ($300.00) per
                  month. EFFECTIVE JANUARY 1, 2000, PARTICIPANTS WHOSE ROLLED
                  INTO BASE COST-OF-LIVING ADJUSTMENT EXCLUDED FROM PENSIONABLE
                  EARNINGS PRIOR TO JANUARY 1, 2000 EXCEEDS ONE-HUNDRED FIFTY
                  DOLLARS ($150.00) PER MONTH SHALL HAVE SUCH EXCLUSION REDUCED
                  PROSPECTIVELY TO ONE HUNDRED FIFTY DOLLARS ($150.00) PER
                  MONTH. The preceding shall be modified for Participants
                  covered by a collective bargaining agreement that provides for
                  a deviation in the method of determining normal wages and
                  salaries. Effective August 11, 1986, the amount of any
                  temporary reduction in any Participant"s salary will be
                  included in Pensionable Earnings for pension purposes;
                  provided, however, that the temporary reduction included in
                  Pensionable Earnings shall be reduced by any subsequent salary
                  increase.
<PAGE>   2
                                       -2-


         IN WITNESS WHEREOF, Transtar, Inc. has caused this Amendment to be
executed by its duly authorized officers this 1st day of December   , 1999.

ATTEST:                                         TRANSTAR, INC.


By   /s/ R. N. Gentile                          By   /s/ J. W. Schulte
  -----------------------------------             ------------------------------