Had a good experience hangin' out at Jake's Auto today,gettin' the GTX dyno-tuned! If the correction factor they have is correct,I'm pretty happy with the results! 1st pull(baseline)resulted in 412hp @ 6,000 Rpm. Tq. was 392 @ 5200 rpm. After several pulls,and jet changes,and 1 timing change,going from 37 to 39,the best numbers were 422hp @ 6,000 and 408tq. @ 5200rpm. Jetting started out at 82p and 90sec. With "best" results,they were 82Pri. and 81sec. To me that is pretty strange,since I'm running a PV in the primaries! Also swapped the 850 Holley to a Pro Systems Holley 1000cfm. It made 422hp @ 5900rpm and 411 tq. @ 5200, but with a A/F ratio of 7.99! Sounds like with a GOOD a/f on the bigger carb,my little 448 would pick up some extra HP and TQ! Had a lot of fun doing this,and I actually got to turn a couple of wrenches,and get my hands dirty! Forgot to mention,the ambient temperature was 83-84 degrees,and 40 humidity. Pretty warm! I'd like to thank Gary Jacob,his son Chris,Tim,and Steve,who operated the dyno,and made the adjustments. Thanks guys! BTW... with their RWHP divided by .72 formula,the hp at the crank comes out to 586! Thanks for taking the time to read this! RandyB. One more little thing I forgot to mention,the engine made 3-4 more hp with my K&N filter and X-Treme top on!