Nice Cutlass...been an Olds guy my whole life so I would definitely drop in another Olds motor but any G body I was building would get a factory engine no matter what GM brand it was. You would save a lot of time and money going with a 350 it would be pretty straight forward. Thinking if you painted your front and rear bumpers to match the body it would look even better and more modern. Hard to beat the look of an Olds engine in a Cutlass.