Interesting. I'll admit, I know nothing about all the varieties of bearings. I did just watch a Steve Morris video where he spoke about bearing clearances. He had one a touch big or small (don't remember) so he was ordering the next size up and only planned to use half of it. This would essentially give him the clearance ne needed. I've never heard of mixing bearing sizes, but if anyone knows, it would be him. But he also builds 4000HP engines that get torn apart very often. Might not be a good idea for a street engine. Do you know what the clearance is on a factory 6.4?