Other than a new oil pump and pickup, I would probably not TOUCH the bottom end. The lowest-budget parts are the ones already there! Plastigage the bearings and send it.
Hey thanks for all your info man. Question on this. I want to tear the whole motor down so I can bring it in to get hot tanked. The amount of sludge I saw makes me really want to do this, also I want to get a good coat of paint on her too. So, your logic about the bearings makes sense, but I am wondering if I can tear it down, inspect the bearings, and if they look good, reuse the bearings? And so the same with the rings. It would save me probably $200 give or take, and every penny counts on this build. But not sure if its worth it..
Also, reusing the convertor from slant 6 is a cool idea I had not thought of. I didn't even know that was possible. I think I'll do this, especially if I may be upgrading down the line with a different rear end, and changing the converter to match. Question, if I am rebuilding the 904 I found, is it a bad idea to use the old, used convertor with the rebuild trans?