From what I read he has access to the rocker area so using an indicator to determine cam lift won't be an issue. The only problem I see is that the vanguard cheetah cam normally has around .308" to .310" lobe lift, and his cams have .304" lobe lift, which isn't much difference and might be hard to catch if he has a worn or cheap indicator that isn't very accurate. Especially if the cheetah cam has wear, or someone takes a few thousandths off the lobe lift to make it appear legal.
Are these sealed spec engines, or are people allowed to build their own motors? If they are supposed to be sealed motors built to certain specs and cam timing, you could use the same method used to degree in racing camshafts. Use a degree wheel and check the cams for intake opening/closing to determine the intake lobe center and total duration. It would be a little more work, but it would be easy for me to spot a different camshaft this way.