Here's a different cylinder head choice and a better block choice as well. Block can be made to go 4.125" bore if you want to build a big inch 4 cylinder. I think some of the earlier 181's had a 2pc. rear seal, I was going to buy one off of ebay and tool up to make it fit the block. Blocks can also be made splayed cap or standard 4 bolt main, but billet either way.
