That casting number shows as 69 to 77 350, 2 and 4 bolt main, truck, pass car, and corvette. It also was block for 69 z28 302. It may be a 327 if someone put a 327 crank in it. There were large journal cranks. The only way to know for sure, is to get crank number, or measure the stroke. And it may be a bastard motor. I've got 327's from engine rebuilders, that were 350 blocks. Nothing wrong with it, just makes it hard to positivly identify without crank number, or actually measuring the bore and stroke.