318/360 heads,with thumper cam

Shaving the heads is a pain. You have to mill the intake to match the heads. If it is done improperly it will leak coolant. The cam you have is fine if you have 9.5 to 1 compression or more but won't perform very well at 8 to 1. I would determine if you have stock pistons or not before you decide to do anything. Just measure how far they are down the bore at tdc.