A few years back I modified a manifold by slightly opening up the bolt holes and then made some wedge shaped washers to compensate for the different angle. That worked. This motor Im working on now has been modified one way or another for many years. I have a pair of new head gaskets and some intake gaskets so I was just going to clean up the vortech heads and put them on. Still have to figure compression ratio, pushrod length, etc. but the basic idea is to do this with parts on hand and spend zero cash. So my next question from your response is; are these heads prone to cracking?