<PAGE>   1
                                                                    EXHIBIT 10.4


                 THIRD AMENDMENT TO PURCHASE AND SALE AGREEMENT


         This Third Amendment to Purchase and Sale Agreement ("Third Amendment")
is entered into as of the 10th day of November, 2000, between MURRAY INCOME
PROPERTIES II, LTD., a Texas limited partnership ("Seller"), and IRON MOUNTAIN
RECORDS MANAGEMENT, INC., a Delaware corporation ("Purchaser").

         WHEREAS, Seller and Purchaser heretofore entered into that certain
Purchase and Sale Agreement dated effective as of September 25, 2000, as amended
by that certain Amendment to Purchase and Sale Agreement dated October 25, 2000,
and as further amended by that certain Second Amendment to Purchase and Sale
Agreement dated November 2, 2000 (said agreement as amended is hereinafter
called the "Agreement"), and now desire to further amend the Agreement in
certain respects.

         NOW THEREFORE, in consideration of the mutual covenants set forth
herein and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, Seller and Purchaser hereby agree as follows:

1.       Terms used herein with their initial letters capitalized shall have the
         same meanings as set forth in the Agreement unless otherwise indicated
         in this Amendment.

2.       The Approval Period as set forth in Section 1.1 of the Agreement shall
         be extended to and terminate at 5:00 p.m., Dallas, Texas time on
         November 17, 2000.

3.       For purposes of Purchaser's Termination Option as set forth in Section
         5.1.1 of the Agreement, Purchaser hereby accepts and approves all
         matters relating to the Property, and Purchaser shall have the right to
         terminate the Agreement pursuant to Section 5.1.1 of the Agreement
         solely for the following reasons: (i) Purchaser does not receive a
         Purchaser Indemnity Agreement as set forth in Section 7.12 of the
         Agreement in form and substance satisfactory to Purchaser within the
         Approval Period, or (ii) Purchaser's lender fails to approve of
         Purchaser's synthetic lease form during the Approval Period.

4.       The Closing Date as set forth in Section 1.1 of the Agreement shall be
         November 30, 2000, at 10:00 a.m., Dallas Texas, Time.

5.       Except as provided herein, the terms and provisions of the Agreement
         shall remain unchanged and shall remain in full force and effect.

6.       This Third Amendment may be executed in a number of identical
         counterparts, which, when taken together, shall constitute collectively
         one (1) agreement; in making proof of this Third Amendment, it shall
         not be necessary to produce or account for more than one such
         counterpart with each party's signature.

         IN WITNESS WHEREOF, this Third Amendment is executed as of the date
first above written.



<PAGE>   2

                                        PURCHASER:

                                        IRON MOUNTAIN RECORDS
                                        MANAGEMENT, INC.
                                        a Delaware corporation

                                        By: /s/ Garry B. Watzke
                                           -------------------------------------
                                        Name:     Garry B. Watzke
                                        Title:    Vice President



                                        SELLER:

                                        MURRAY INCOME PROPERTIES II, LTD.,
                                        a Texas limited partnership

                                        By: Murray Realty Investors IX, Inc., a
                                            Texas corporation
                                            General Partner

                                            By: /s/ Mitchell Armstrong
                                               ---------------------------------
                                            Name:   Mitchell Armstrong
                                            Title:  President