Just curious, is a Pontiac Grand Prix 68-72 frame interchangeable with the regular A-body frames like Cutlass, Chevelle, Skylark, Lemans? Thanks.

 

no .
Their 4 inch longer in the front.
Just like the monte
but you could cut the 4 inches out of the front horns

 

Well, a 1968 Grand Prix is a B-body, not an A-body.
The 69-72 GP and 70-72 Monte have a unique wheelbase and thus a unique frame, as noted above.

 

Believe some of the "extra" length, like the Monte Carlo, is between the front control arms and the firewall/cowl. As well as in the front horns. From what little parting i've done on 69-70 GP, remember the engine crossmember, that goes under the oil pan is different too. I've heard first gen '70 - '72 Monte Carlo's referred to as G body, although that usually makes me think of the '81 - '88 last hurrah mid size cars. Guess Fisher was the entity, who decided on what letter series they were called.