Here's what I can tell you about my RB block. I should be getting it from the builder very soon. It went back last August due to a machining / core error in the oiling system. The oil port in the front of the block used to bypass an internal pickup intersected the oil pump drive shaft bore causing it to suck air. The only other issue I had was I ended up running a tall roller lifter due to the bronze bushings being tall.

What I can say is that Bill Mitchell was very helpful in getting my issues fixed with the oiling system and great to work with. My block was purchased in Jan 2017