up to 87 760 and 740 were pretty much the same, IF they came with the 2.3LTIC.
760's came with leather, 760's had the automatic climater control, everything power, while some 740's had manual sunroof, part leather seats, small stuff like that.
in 88, 760 got the Independent rear suspension, and a different nose, the one that the 740's got later in 91 or 90 i belive.
with the new nose came an aluminium hood with hidden wipers, a different sloping winshield, IE the older windshield ones will not fit on the newer ones. in 88 the 760's also got a brand new, much more eye pleasing dash, with 6 speakers (2 on the dash, 4 usual in the doors)
as for nivomats, i dont know when 760's got them or if 740's ever had them.
ABS controller was mounted in the trunk with earlier models, (85), and was later transfered to the engine area, (next to the battery)
anything else?
who knows...i've found out from experience that Volvo changed small things year to year...
for example, we had a 85 765 with ABS and it used 14' tires...
those tires cant fit on 87 760's cuz of different caliper size...also ABS...go figure.