A darned good question... the point I was trying to make to the OP was that you want to be well up on the torque curve of the cam when the TC stalls, not well up on the HP curve.
For 'up on the torque curve', I go by mfr's RPM ranges; they are generally spec'd for the lower RPM end of the range where the torque is well 'up on the curve', and for a 'typical build'. And I then think of how the engine will vary from a 'typical build', and maybe modify their range ends.
It would be educational to see if there are curves on cams and see where the lower end of the mfr's RPM range is on a 'typical engine' build torque curve..... but I suspect that data is hard to find. (I see a few for Comp cams but the torque graphs tend to start above the lower end or their RPM range...so that's no use.)
