First thing you do with any mopar engine is: get a sonic test done. Mopar are known for end of a production run to cut back on metal ( thin wall casting). Sonic test will show you wall thickness. Between the water jacket & piston wall. When making the block at the factory if there is a core shift. The clearance will be less. In other words: you are limited to what you can overbore the block. In '72 late & in '73 Mopar put out alot of thin wall casting blocks!!! This info is not limited to Mopar only. Chevy put out some bad 427/454 blocks.