
Most of the 2nd gen ('68 - '72) GM 2 door A Body frames can be made to work: some model years have slight differences (especially '72 Pontiacs) and convertible frames have additional reinforcements (as I recall 2 door Judges were built on convertible frames). '68 - '72 El Caminos us a different frame, and '70 - '72 Monte Carlo frames won't fit.
If you plan on doing a handling suspension get a convertible frame.