You would be better off buying both cylinders, you don't have much left on the 66.25, and you don't want to run 2 different size pistons. Ive seen alot of good deals on sets of them on here so a search in the for sale section on cylinders or jugs. Is the crank still good? If its stock you may want to get a new one just to be safe you don't want to get it back together and have it go out on you, you should go with a 4mill, I have a stock head and stator cover if you need it, Pm me if you need any help or need any other things i'll be glad to help you.