Budget drag car… B-Body or A-Body?

A body has all the advantages. Lighter (Better results with building a small block.), shorter wheelbase (Better weight transfer/traction.), probably easier to get parts (body & chassis) for and you already have your experience with them.

Biggest disadvantage I can think of is the '72 & earlier small bolt pattern rears and lack of 8 3/4s in '73 & later models. But the 8 1/4 isn't that bad.