[Tom Vogel]

I would say that 72 is the 'Most' desirable because of the increased amount of options available. As to smog equipment, these vehicles are smog exempt in most states.
As far as keeping them original, I would think these are more on the line of a tri-five Chevy than an early Corvette or an LS6 Chevelle (thank goodness). That said, I wouldn't personallly cut an original 2wd up beyond recognition either, because they are sought after for a reason. If I wanted a radical custom, I would just get a body and start from there.