A well built 4L60E from one of the sponsors (Performabuilt, FLT, RPM, Jake's Performance) can handle 500HP with no problem. A stock one will not handle it for long. If your budge allows $2000-$2500 you have many choices.
If you plan on a adder (turbo, supercharger, Nitrous) which would boost you well past 600HP, you may want to consider a 4L80E.
If your budget is tight, you might consider a TH400 as even a cheap stock rebuild will easily handle 500+HP. Just no overdrive.
Last edited by mrvedit; 03-15-2013 at 02:30 PM.