All A, B, E cars have very similar unibody structure. Just stretched here and there.

B and E interchange suspension wise. Just e-body rear springs have 1” shorter rear segment so the spring doesn’t poke out the rear valence.

A bodies interchange B/E spindles, steering gear, bushings, ball joints (year & brake dependent). And most suspension piece look very close to B/E bodies but vary 1” or less deminsion wise.

The true post cars are a plus. But 67-69 Abody posts have the same poorer wheel room as the 67-72 Darts

108" WB
70-72 duster demon
67-69 Barracuda coupes

Can fit 245/45/17 tire front with right backspacing. 275/40/17 if you simply cut/fold the bottom front corner. And same size or larger rear. On the two model groups above.

E-bodies can fit 275/40/18. I think Ariel got 305’s on his Cuda with just lipping

Imho, the best light/strong chassis would be the 63-65 valiant sedan at 106" wb. But you'll have to fender flare it. Next would be the Dart of same era.

I don't see why something like a massive 112" wheelbase is an advantage over the extra 200 lbs of a 68-70 B-body on a road course. There's Miata, 911, and smaller wb that perform quite excellent. IMHO, 108 and 106" WB is long.