GM used the same block for 302's, 327's, and 350's so, any block will do. Just as 427 and 454 blocks are the same. Some of the older 327's had a small journal crank, and will not be interchangeable, but those cranks are hard to find, so you're better off using a large journal.

Your other option is to buy a set of aftermarket splayed caps for a 350. They are stronger than straight bolted 4 bolts but installation may be expensive.