I would assume that the 740 in the salvage yard does not have power seats. -and I have yet to see a 740 in person that came equipped with power seats from the factory. The 760s and 780s all had power seats if I recall correctly, and there's a possibility of 3 or so different seat heater systems that could have been installed (depending on market, climate, year, model, etc). Off the top of my head, I think there were two different single-stage heat systems, and a dual stage setup. It might be a plug & play swap, it might require changing the console switches to match the seat heater, and/or splicing a few wires. I believe the manually operated front seats in the 740s all had the forward height/tilt adjustment (vertical lever against the center console) as standard equipment starting in '87 and previous to that it was only available for the drivers seat (and not the passengers seat).

I would strongly encourage you to consider swapping the seat covers if you're interested in keeping the power seats. Otherwise the non-power seats should be a direct bolt in. Swapping the seat covers isn't that difficult, as long as you have some good strong diagonal cutters for snipping the hog-ring clips and have a stash of zip-ties to replace them afterwards. It's much easier to do with the seats removed from the vehicles and sitting side by side on a wooden workbench. The headrests come off by pushing on two release tabs through the fabirc while lifting up on the headrest. The seatback section comes off like taking off a t-shirt (once you have the 6 hog-ring clips undone at the base where it contacts the lower seat cushion).

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 249k miles.
'88 Black 780, PRV-6, 145k miles.

760 and 960=electric seats 740 and 940=manual seats. All 900 seats will direct bolt in 700. 240 seats will not work in 700 or 900. As far as wiring, part of post from mapleleafer Feb 4, 2004:
"There are a few variations of connectors, heater elements and thermostats between the 740/760 to 1990, the 87-91 780, and the 740/900 cars from 1991 up.
EARLY TYPE 3-wire system, used until 1991 or 1992;
Inputs: RED/BLACK-power, BLACK-ground, White/Black- signal from console switch.
Thermostat; usually black and marked with upholstery type, has 4 pins.
LATE TYPE 2-wire system, used since 1991 or 1992;
Inputs: RED or RED/BLACK-switched power, BLACK-ground
Thermostat; coloured other than black, most are Green. Marked with upholstery type, has 3 pins."

--
Keith in Maine - 1990 740GL Wagon 245k AW70L B230F Red Block 8 Valve Non-Turbo Rex/Regina Non-EGR R-12 A/C

See the 700/900 FAQ. They should be interchangeable, but you may have to modify the electrical connectors.