I am about to drop in a 481 (454 with 4.25 stroke and .030 over bore) into the 74'. Have been running a bone stock smog 454 with a Q-jet which performed outstanding off and on road. The 481 has a Scat rotating assembly, H-beam rods, JE pistons, and 781 early chevy heads with 256 cc intake runners. Cam is .516/.516 with 220 duration @ 50. 9.0:1 compression. I was initially planning on going with one of the Edelbrock 850 CFM performer Q-jets getting it calibrated to this particular configuration. I have been warned that even this Q-jet will significantly limit HP. Because of the outstanding off-road capability the other Q-jet provided I am OK with small decreases in top end HP,, less than 20. However, the guy at the dyno shop here said they ran healthy 383 first with the Edelbrock 850 and then a mechanical secondary 750 holley and went from 390hp to 470hp..... Pretty significant! If I ran a holley, I would have it massaged by a local performance carb shop. They have mentioned running it with spring loaded needles and I would run a fuel regulator set at low (1-2) psi for the rocks with a bypass valve for everything else. Also, I have been advised that with a holley I would be able to get away with more cam and still have the carb like me,, like .540 intake which would obviously free up more power. I just dont want to have a DOG at angles, which is what I was dealing with the previous Carter style (Edelbrock) carb. Big rocks and elevation were just way to much for it... If anyone can help solve this delima I would appreciate it. The truck is used as a DD, in the desert, rocks and towing.....it is the only ride.