How far can I deck the early Cummins block? I see they make .020 thicker gasket so I imagine at least that far. My thought was decking the block to bump up compression by reducing piston to head clearance. But if I over decked the block then set my clearance by milling the piston tops then I could also reduce bowl volume and further increase compression. Even if I could get away with decking it .030 or .040 I'd be in the money I think