Just got back from my machine shop and they want to put one sleeve on my 455 block. This would require a 4.3 something bore to accept that sleeve. They assure me it's okay but I am skeptical since a .60 overbore is usually considered not good from what I gather here. I do not think he has sonic testing equipment . You seem to be very knowledgeable on matters such as this and I would certainly appreciate any input you are willing to provide. The owner of the shop is very nice but somewhat casual-says he does it all the time. He mostly builds high end truck pulling motors. Any opinion would be greatly appreciated. Thanks,Paul