[Rick Parker]

It sounds like the either the block face or the cylinder head faces have had a significant amount of material removed therby reducing the depth of the machined alignment dowel holes on the faces of the block and head. If you have dial calipers, measure the the depth of the machined receiver in each face plus thickness of head gasket, this dimension should be greater than the length of the dowel itself.If this checks out, you may be running out of thread as you clamp the head down, be sure you have the correct bolts/studs. Lastly if you are running domed pistons be sure the deck height is set right.

No room for error here.........good luck

Rick...............