I use to figure ands use one jet size up on the Holleys going from LACR to Orange County or Bakerapatch. Going to Vegas or Inyokern I would leave it alone,jet it up two sizes at Fremont, Sears Point and Sacramento.That was on Daeco race gas available back then.I would be willing to try one jet size down(leaner) for each 2000 ft increase in density altitude measured on a good weather station