how can ya tell??

I've found it is stamped on all the small blocks I've seen on the drivers side front just below the head surface. Only problem is most times they didn't stamp it very good and it's hard to read. You'll most likely have to scrape the paint completely off and use brake or carb cleaner on it to even find it. My 79 360 block is stamped so lightly it's barely readable but it's there. The numbers on the side are always easier to read (unless crusted with grease and rust) but like you say there's not much room there to see. The ones on the front are easy to get at at least.