One potential "gotcha" can be the higher current draw of substituted opamps vs the originals. If swapping out only a few, no biggie...but if dozens/hundreds of chips are swapped out, the OEM power supply may not have enough moxie.
One other thing to ponder. Many desks, etc did NOT use sockets for the chips, so you will need to invest in a quality vacuum desoldering station (and learn how to use it! <g>) to avoid damage to the circuit boards.