I have a GMPP 350 with cast aluminum pistons its had its problems but nothing with the engine just goofy things i must have missed working on it till 3 in the morning those days. I am thinking of upping the compression on it and giving it a little hotter cam to it. Its the 350/290hp/326tq engine. As far as I see for the HO version they just tossed vortec heads on the sucker and made it a high output and a different cam. Are these aluminum pistons even worth it?
How much of an increase are you planning? From what I read in the link you provided I see no reason you couldn't bump it up to 9.5 or 10 to 1 compression. That is about all you want for pump gas anyway. A cam upgrade would be good too but I would stay away from nitrous and would also keep the redline at 6000 RPM or less when you do choose a cam.
I want to get to atleast 380 hp version of the 70 z28 engines. I think some vortecs with upgraded spring and a good valve job with a cam that gives more grind would get me there. I think 9.6:1 compression is as far as I want to go with compression since I dont want to bust the wallet.