A newer short wheelbase panel van may be another option (especially if you want to revive the van idea!) if it weren't so aggravating to swap engines in (It must be the crazy kicking in, but why am I thinking Mid engine B150?) If you can find one, a Rampage/Plymouth Scamp GT is relatively easy to convert to RWD and is going to be the lightest platform you could start with. Heck, you probably could make your goal with one of those with a 383 or a 400 on pump gas with a powerglide.
