A 327 is a 350 with a large journal 307 crank. Easy to find those parts for this build. 4 bolt 350 sbc's are not as strong as a sbc with splayed 2 bolt caps and girdle. Unless you machine the block for billet mains
I am not a specialist, but according to sbc history and technical books, the first 4 bolt main in production was the 1969 z28 302 4 inch bore, 3 inch stroke.
Steve
I believe you're right. I can still remember the parking lot speculation about the "new" Chevy 302 when it came out. I didn't realize for some time that it was the "same bored 283" that we all called a 301
