Engine rattle

Today we started our engine, 383 mild build. We ran the engine at 2000-2500 rpm, 10 degrees base timing, open headers, 50 psi oil pressure(with break-in additive) at 180 degrees for 30 minutes. Shut it down and checked for leaks. We installed a pair of mufflers and ran it for another 25 minutes. It has a rattle from the right side that we thought was lifters needing to pump up (sounds like valve train). We pulled the valve covers to check for loose parts and found that we could move the #8 intake rocker arm enough to get a .025 feeler gauge between the rocker tip and valve stem. We switched rocker shafts and push rods and had the same issue. We pulled the intake and there is no visable wear(can't feel anything with your fingernail), the lifters have a nice pattern in the center, the cam has a nice pattern on the lobes. We used a dial indicator and the #8 intake lobe has .003 less lift than the #6 intake lobe. All of the lifters on the drivers side were pumped up, 3 of the lifters on the pass. side were pumped up. Do you think we have an oiling problem, lifter problem or do we have a cam problem? Any suggestions would be great.:banghead::banghead::banghead::banghead: