I dont think you are going to get much help going after people that did actually give you an answer. Your question was "does anyone know where i can get some forged turbo pistons??". You them procede to ask " OR can i use the flat tops forged and use a larger headgasket to bring compression back down or does that screw up the reliablity that i am looking for?".
You did get you answer. Wich was had you taken the time to do a little searching around YOURSELF, you would have come across several forged piston options for the turbo L28.
FYI - More searching will show a factory L28 Shortblock is capeable of 400whp+.