How much of a performance gain can i get with premium forged pistons like these

Keith Black/KB Pistons IC884KTD-020 - Keith Black ICON Premium Forged Piston and Ring Kits - Overview - SummitRacing.com

Will there be a MPG lose with something like these.

Or is there a better brand, i dont know much about pistons and stuff like this

If you're planning on splitting the block then go all forged internals with a supercharger. The pistons alone aren't going to help much by themselves.

Or.....
Call it good and buy yourself some of these.
http://t2.gstatic.com/images?q=tbn:V...fuzzy-dice.jpg
Just a thought........

Would you be paying someone to install these pistons, cams or other internal parts your asking about?

Yes. If or when i decide to i would have somebody else to it. I dont have the tools or anything like that to do it myself.... Plus im afraid of breaking or messing something up.

I would decide on a performance shop that i wanted to use then ask them what they recommend.
If you take a cam and pistons to a mechanic and ask him to install them he will do just what you ask. the first time you start the truck and your valves start poping holes in your pistons the mechanic is going to say "you brought me the parts."