It is virtually a bolt in.........the four cyl cars and v8's are the same. You will want to use a double hump transmission crossmember that you can get off of any V8 car (it comes out with two bolts) and use 79-93 v8 motor mounts, that also bolt on.
For an
oil pan you will need to use one of the double sump models, the one on your 78 is a front sump probably, but any double sump pan will work. For exhaust you can use any header or manifold that a regular 5.0 Mustang accomodates.
The four cylinder cars are actually preferred for these swaps as they generally haven't been abused, and the torque boxes in the back are not torn loose, as are many 5.0 cars that have been hammered.
You probably already have an 8.8 rear in the 91 (the rear cover is square on all sides, the weaker 7.5 has round sides on the cover.) You can use any 79-93 Mustang or Capri driveshaft and just need to make sure the front yoke is compatible with your C4. Any driveshaft shop can change it out for you if not.
From that point on it becomes just like any other 5.0 mustang, regular shifters and all will fit. For a radiator just use any 5.0 radiator, and since your 78 engine has a V belt pulley system you will need to use a V belt power steering pump if you have power steering. However, I would use a manual rack and eliminate all of that.
Wiring will be a little challenge depending on what ignition system you use and what components you use, but it is still pretty straightforward.
Ford really gave hot rodders a gift for the 14 years they made these fox platformed cars, everything just drops into place. Good luck.
Don
Yep. It’s pretty sad.
Dead!