You’re not thinking right. You want to take stock cylinders and bore them to 66 leaving you one more bore (in reality) or possibly no more bores, then pay for porting, then domes and pistons. Why?
buy Driveline kit direct from DL and keep your crank (stock Yamaha cranks are awesome or buy a used one) and build a 392.
go to the product review section of this forum and find a post by Mailman on his 392.
its a no brainer