He's coming from a Mazda 3 (106" wheelbase), a b-body is already quite a bit larger (relative overall length of a Chevy Suburban, 117" wheelbase), and a c-body is even longer than that (120+" wheelbase). You're talking back when a 6 second 0-60 time was impressive for a Hemi Cuda, and HD leaf suspension, brakes (big 11" drums!), and front/rear swaybars were voodoo other than on T/A cars and police cruisers. It was impressive back then, but a V6 minivan would probably outperform that Polara on the road course today..

You can get a b-body well into the 3400-3500# weight range, with some basic fiberglass parts, let alone aluminum heads, intake, etc. If you're going to be placing 10K + in suspension, wheels, tires, and brakes; why start with something that is exponentially more difficult to acquire parts for and with a dramatically smaller community. You'll have 15-20k into either car EASY! Honestly, an a-body is probably the better starting point, but a b-body is fairly capable (if lightened up!). C-body would be different, and the initial investment would be lower (obviously, would be dramatically less valuable in the long run , regardless of modifications). Good luck with whatever direction you choose, I'm sure it'll be a tough call either way.