Well if you are handy with a torch or welder or have a deep pocketbook you should be able to fit most anything in there.
Actually if you are wanting to put a Pontiac engine in you can go up to a 455 since the block dimensions are all the same. But it will take some fabrication since the only V8 that was put in your car from factory was a Chebby.
Oh BTW welcome to the boards! Lots of good info here. I see you are from ND too. What part?
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North Dakotas fastest REAL GTO
10.10 @ 131 MPH in the 1/4
Hoping to get it back together some year.
www.jandjrepairandrestoration