As Ed says you have a multi part question here and there are no for sure answers.
But have you checked into the difference between blower/nitrous pistons?
First of all they are never gas ported, the top ring lands are dropped down on the pistons and the domes are usually thicker. The reason for this is that a blower or nitrous creates a lot more heat in the combustion chamber and that transfers to the ring causing a not so good seal and if the tune up is off it will detonate and burn the piston between the top and the ring.
I don't know much about nitrous and i don't know how much you can get away with useing regular HP pistons. But i do know about blown applications and as us7race says you better have your tune up right or you will melt it down. If i was going to build one i would go the extra $100.00 or so and buy the nitrous piston, it would be a good investment.
just my .02
Zip.