90’ Grand Marquis 5.0 Build

I think @LaserSVT might be able to answer this but if not, maybe knows who can.

I can tell ya that "any" motor swap into that car will likely not be financially feasible but other than that, you can put pretty much any motor into any car.

Not much is usable off it. You are pretty much going to spend more money searching for all the odds and ends you will need. The ECU is batch-fire, and the wiring is speed density as well. Injector harness is pinned incorrectly for the non-HO firing order. The heads are E6SE heads, the intake and Tb are the early 1986-style Mustang manifold which is tiny. Cam firing order is the non-HO order.

I wouldn't buy the car for a 5.0 swap. Buy yourself a 96-01 Ford explorer/mountaineer 5.0 engine and then find a clean 4-cyl and do a carb swap setup, or if you want EFI you'll have to search down the expensive 5.0 Mustang ecu and wiring.

However, If you already have a 1998 GT, just do a 99-04 PI head/cam/intake swap to that car, with an aftermarket plenum and TB and full exhaust and you'll be at the 300 crank HP range anyway. I don't even know why you'd bother with a 5.0 pushrod swap unless you are swapping in an AL-headed 347 or something like that. You can probably buy the PI swap parts for about what you'd pay for the marquis.

PI swapped '98 2V 4.6L > Gran Marquis 302 engine