If the engine revs to 6200 on the stand, that tells me nothing in the engine is terribly wrong. The fact that it won't read that high on the track leads me to believe there are several things that could be less than right.
When things were not going right, the 1st thing I did was check the compression pressure. You need a good gauge, Pep Boys doesn't sell one. I used a Snap On. Expensive, but the best. I have no idea what a good compression reading on your engine would be, it's kind of a comparative thing, check yours, check your friends, compare the differences.
Timing, check yours, ask around, what's good?
Spark plug, it's important, heat range, ask around, what's the competition using.
Jetting, again, ask around. From your responses, I get the idea that your running really lean. Something to check. Too lean can cause detonation, detonation ""kills"" HP. Detonation is caused by excessive heat and/or pressure. In the shop, on the stand, there is very little heat and/or pressure being generated, result, no detonation, but put it on the track, with a load, and you can get detonation.
EGT (exhaust gas temperature) gauge is the perfect way to detect detonation. In my experience, there's no better way to do it.
Calculating CCs. You can do it, you need to know how many ccs in the combustion chamber, but it's best to measure it.