With a zero deck and a set of FelPro 1003 head gaskets your quench should be just about perfect - .039 or .040.

At the Mid-West nationals in Sprigfile last year I saw sm GM Vortec racing heads. They had center and perimiter valve cover bolt locations and were drilled for both Vortec and conventional intake manifolds. No idea what the price or availability was. The GM guy working the booth was witless.

Several companies offer the tools (cutters) to make the modifications. Check the ads in Chevy High Performance. Or, for the same amount of money you can have a performance oriented machine shop do the work.

Vortec heads are good performers. But they are not as cheap as some folks think. It takes several hundred bucks to get them ready for a high lift cam. If you already have a performance intake and valve covers and are simply upgrading you have to factor in the cost of replacements. Vortec heads also use self aligning rocker arms. If you want to run older rollers you need to machine the heads for guide plates and enlarge the pushrod openings.