I think GM Corporate just put anything they could in the BOP's.. only Chevys were gaurenteed to get Chevy engines.. I'v seen trans am's with oldsmobile engines, as well as other pontiacs of that time period.. looked at a 1978 Cutlass cruiser custom a few years ago.. woulda made a sweet sleeper with a 455.. thought it was a 307 or 350 olds. but when I popped the hood, I found a SBC and the valve cover emissions sticker said Oldsmobile corporation .. weird because the '80 Cutlass supreme my dad had years ago, was powered by a 307