Thank you all for this great information!
Thanks Tony, I thought there was a scientific reason why new tophats required 30 thou over dimensions. BTW, after I took bare block to machine shop, they talked me into lots of easy DIY stuff but I let them do it and cost went up big time ! Next time, I’ll stick to my initial “just install the tophats” request. They saw me coming, here comes ‘another bare block type guy’. However, at least now my crank is balanced (w/damper) and 10 thou over, clock decked (with timing cover), they installed my pistons, and used better grade racing rings, and the two tasks I was tentative about; the thrust bearings; they got the clearance correct and the rear main oil seal rope (no leaks). Plus, shop installed original oil pump and my new repro brass dist drive; and the offset key/dist drive was set right (I screwed that up my last DIY build). The head was done at CW (Dick M). So total engine $ was around 10thou$ .