For what it's worth this is my 2 cents. A wise man said if you have too much bearing clearance you alone will know. If you don't have enough , everyone will know. As long as bearings are available or clearance isn't out of this world, it should work fine.Same with rings. 4.5035" file fit in your bore may work a blower motor wants a big gap anyway. I doubt it will know the difference. The biggest issue here is you are questioning your engine builder. You both need to be on the same page. If you don't trust what he's telling you asking on line is a crap shoot. Lots of knowledge, lots of misinformation, just need to know how to sift through it.
Doug