Twin charged 6.2 cam question..
 

Putting together a 6.2 fo my 06 gto, so far I have a 50k mile short block from a gxp, going to do arp everthing on the bottom end, and studs for the head. Running a set of trick flows255's And a cx racing twin turbo kit, but mainly just using the piping. Planning on getting a set of turbonetics. Intake will be a efi super victor with an elbow. Question is how big of a cam can I go without compromising valve to piston clearance? I didn't plan on going over .650 anyways but just from what u have read it seems that anything over .620 is really cutting it close....opinions???

You mean twin-TURBO... twin-charged is an entirely different animal.

Your tfs 255's flow ~360cfm @ .600", and ~380 @ .700", so you are going to want all the lift you can get. Flycut the pistons, if necessary. But you want to capitalize on that airflow.

As for actual cam specs...? Call any of the big cam guru vendors on this site... Cam motion, tick performance, mamo motorsports, texas speed, tooley racing, guerra group... to name a few.

Lift has almost no effect on piston to valve clearance
Duration is what will cause issues

Like said above
Contact a sponsor that specs turbo cams and see what they reccomend
Better advice than youll get grom someone on here usually