Here is the deal: you need to find out if they swapped K-members when they did the 4-swap. See, the Fox's use the same K-members for the 4 cylinder and 8 cylinder, but use a completely different K-member for the 6 cylinder. The 4-cylinder mounts are simply built on top of the v8 mounts.
The 2.3 is feasible (is that spelled correctly), but keep in mind that an aluminum-headed 302 only weighs about 45 lbs. heavier than a 2.3 with the turbo and all on it. Remember, the 2.3 doesn't get an aluminum head unless you get an ARCA head (at LEAST $2500 complete). I believe Esslinger makes their own aluminum 2300 head, too. Hell, they may even make the ARCA head.....dunno, I can't remember.
They probably used a 4-cylinder T-5 to do the swap, or used an auto (a4ld). The T-5 has a different pilot bearing than the v8 T-5 IIRC, but use the v8 T-5 because the gear ratios are closer together. The 1-2 shift in a 4-pot T-5 is STEEEEEEEEP!
You can get a set of GT-40P heads for the v8 pretty cheap (I have seen them at swap meets for $350/set), but remember that they take a weird header due to the angle of the spark plugs. If you look, you could probably find a set of aluminum heads (complete) for around $550.
If you find a T-5, anything '86 and up is a World Class IIRC, but they are still only good to about 300 lbs./ft. if they are in great shape.
The 6 cylinder would have had a 7.5" rear, I am pretty sure, just like the 2.3 (unless it was a turbo 2.3, like in the SVO). They are okay (if you are making less than 10 hp), but the axles twist pretty easily in them. Find an 8.8 out of a T-bird (good gear, trac-loc, disc brakes).
-Les
BTW, please verify all this stuff elsewhere as it has been a while since I did anything with a 2.3 Ford. Try www.turboford.com .