I've got a Procharged (m-1) 502 with Lightning marine headers and 50 lb. injectors. Going to install Dart Pro-1's with 325cc runners and a Crane cam #731 (610 exhaust and 587 intake). I'm currently running 5 lbs. of boost, how many pounds of boost can I expect to loose???

I don't have the exact answer but I know what's going to happen. The reduced restriction of the better heads and cam will lower the overall restriction presented to the blower. This will lower the blower's discharge pressure and allow the blower to move more air into the engine. More air, more cylinder pressure, more power. The lower discharge pressure also means lower charge air temperature. Who cares about boost in the intake manifold?

Should'nt I bring the boost back up to 5 lbs for more Hp?

I changed from a stock HP500 cam to a cam similar to yours and put on a set of pro 1 heads with exhaust ported and I lost 2 psi.

The change alone will result in more power and less bost showing in the intake manifold at WOT.

Sure, the changes PLUS bringing the boost up will definitely result in more power.

The assumption is always that you should increase compressor RPM to get back the boost you lost. But you already have higher cylinder pressure, that's why you have more HP. Detonation is the limit; cylinder pressure and charge air temperature the variables.

If you bring the boost up 2 psi, the discharge pressure will likely go back up to what it was before the head change, but now at a greater air flow rate. Only by looking at the compressor map could you say whether the charge air temperature will be higher or lower than the original setup.

But if you really want to increase boost, you need to create some detonation safety margin because you will have much higher cylinder pressures than original. More fuel, less timing, better cooling for the engine, the aluminum heads, all these add safety margin.

Finally, it would be nice to increase intercooler efficiency as well.

I sent my Computer back to AZM (they did the original map) and had them remap for the changes I made, I also told them I would be running 6 Lbs of boost. I use a two bar map sensor witch senses changes in manifold pressure. For every pound of boost I loose a degree of timing and I believe it will also change my fuel curve.