Just to clearify the head. The difference between a 58mm and 62mm head is the chamber, the smaller the chamber the higher the compression. I have run the stock chamber head on mine with a 63mm bore untill I went with the domed piston. At this point due to too high of compression I had to go with a 63mm chamber to help bring the compression down from 15:1. In your case the 63mm bore with the 58mm head chamber milled .025 will give you around 11.5:1 compression ratio.
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