stock pistons
 

anyone running stock pistons with the edelbrock performer RPM with 2.02 valve or the AFR 185's what lift cam can I get away with?

Depends on the year of the engine. If 87 and up it is not about the valve diameter or lift, it is about duration, the amount of time that the valves are open and when they are open. The beauty of the roller cam 5.0 is that you can run a ton of lift with stock pistons, even the Trick Flow Twisted Wedge heads as long as the duration measured at .050 valve lift is 230 degrees or LESS! I have put AFR, FMS, Edel, Holley, Dart, Trickflow heads on stock pistoned 5.0 engines (87 and up) with as much as .600 lift. We did this by keeping the duration down and not putting a cam in with less (numarically) than 112 lobe seperation angle. (overlap) So as long as the valve springs can handle it and the valvetrain is set up right and you follow these simple rules then lift and valve size is really not that big of issue.
The 86 5.0 had true FLAT TOP pistons! NO valve reliefs at all! the above does not as a rule work on the 86 5.0 STOCK piston!