A 350 would have been born with a 270 if its a 6 cylinder. The Pontiac in the glove box refers to Pontiac MI. It was the 400 series that got the 302 engines. However, as Tim said, almost anything from a 228 up to a 302 could have been installed because they all bolt in. Scrape the flat part of the distributor boss and see if it looks like it is factory machined. If so, The first 3 numbers will be the displacement.
