I would talk to Geoff at EPS (Engine Power Systems)...Geoff is the one that made Thunder Racing what is once was. Ed Curtis is another that comes to mind. Another excellent cam resource is PredatorZ (Mark) on the forums here...he can really point you in the right direction and confirm that the spec's you have been given will meet your desires.
If your cam ends up being over .600" lift...you will be told to get the Comp Cam's trunion upgrade for your OE rockers...the rockers themselves are stout pieces other than the needle bearings that puke over .600" lift.
Also, the person that specs the cam will also be able to tell you the pushrod length (always measure when putting it together though) and what springs you will need. I wouldn't change the lifters unless there is a problem with them...although some of the OE lifters have gone bad after a stout cam has been installed...but there is no duplication of labor here since the cam stays in the block and the heads have to come off for lifter replacement.
Your probably going to get everyone shouting at you to use Pat G...while he is very good at what he does...a cam in an otherwise stock LS6 has been done thousands of times over.
My guess is that you would be happy with a standard tried and true 228/228 on 114*...pretty sure you will end up getting something close to that.
__________________ Bin Laden, Gaddafi, and Kim Jong il all dead within the same year...maybe Team America World Police does exist! 2004 Platinum CTS-V - LS6 with an E Force...and LOT's more to come! 2003 ECSB Z-71 Silverado - 5.3, Comp 265 cam, Pacesetter L/T's, 2" body lift, 3/4 ton torsion bars, Moto Metal 951's, 33" BFG's 1987 Buick Turbo - Beginning the long path towards recovery
Best streetable cam I have ever used is a howards cam 226/232 577/588 on a 115. I even used it in a bolt on 2010ss and the car made 452rwhp.. Prob put this cam in 15 cars. also can easily use single springs.
__________________ 2005 CTS-V, 150 hit of the giggle gas. Twin turbo coming soon.
2004 dodge 2500 4x4 cummins