Can anyone tell me about the stock stamped lifters. I've heard that they are good to 6,000 rpm's. I've also heard that they are only good to .500 lift anything over that I'll need to change. I'll be putting a set of 308 heads with 2.02 valves on my 340 and doing a cam swap, looking for something like 292/292 duration and .509/.509 lift. Stock pistons with a rpm performer intake.