Can a Chevy 350 fit in a 1971 cutlass supreme that has a 350 without changing the transmission?

If memory serves me right, back in the early 70's the Chevy V8 and the Buick V8 shared the same bell housing bolt pattern. The Oldsmobile V8 and Pontiac V8 shared a different bolt pattern. But, back then GM did have a turbo 350 transmission that had two bolt patterns that would bolt to all of their V8's and some of the vehicles were produced with that transmission. Whether or not you have that double pattern transmission you probably won't know until you take it apart.