That's an interesting issue. I'm no motor build expert, but have you thoroughly checked the block and head surfaces for straightness, or maybe the cylinder walls to see if they are out-of-round; those details that the naked eye can't see?

Are your valve stem seals still good?

That's why I'm not doing my own block, those bearing clearences and choice of OEM or aftermarket can be tricky. Then again, if I never do it, I'll never learn. Best of luck as always.

Sometimes, the longer it takes, the better it comes out.