All you need is a straight edge and some feeler gauges. Get the piston to TDC lay the straight edge over the cylinder, measure. Check out the heads sold by Marsh Performance. $1050 pr/valves. You tell them what kind of cam so they can get you correct springs. Heads come to you ready to run. The are an engine shop. If it's not in your budget nothing wrong with using your old heads, gasket match heads to intake, get someone to check spring pressure, but if you have to spend more than $500 on them it's just a waste.