Near future I'm planing to put forged pistons in a ls1 and I'm not sure what size and rod lenght I need or a good company to get them from. Also I'm planing to use trick flow 215 heads will I need to do any custom work to them? It would be great if any one can help me

 

If you plan on reusing the crank just get stock length rods. This is if using stock sized pistons. A seller like Texas speed will have all the info you need on that kind of stuff.
As far as pistons goes mahle, diamond, Keith black, wiseco are all reputable manufacturers.

The trickflows are great head choice, and they should be good to go out of the box as long as their springs match your cams requirements, which again a vendor can assist you.

 

here's the link for TEA which sells the TF heads but can also outfit them with
powdered metal valve guides for stock rockerarm compatibility. The bronze
valve guides should be paired with aftermarket rocker arms. They can also
CNC your factory castings for about half the price as another option.
As the other fella stated sticking with the stock 6.098" rod is fine and will
keep the piston taller which promotes ring stability.
http://www.totalengineairflow.com/pr...ylinder-heads/

 

i like the 6.125 rods. There are many companies that make them and vendors here that sell them, but know that if you use anything other than a stock rod length you will have to get new pistons that are made for the rod length you choose.