If this thread is still "alive", I suggest the OP check out the original Holley calibration for an 80513. Going from memory, that tune above is waaay leaner than what it would have come with. It may "look" right because the traditional 850 that runs better might be jetted similar to what's described, but those two carbs have different boosters, different metering blocks, etc., and are intended for two different applications.