A friend and I just recent had to R/R a 454 and install a 366 into his 1979 GMC dump truck. Originally it had some elect comp on the original carb but installed a 4brl standered Aftermarket Holly carb onto the 366. Now my friend was told that unless he installs the old carb that the truck will never run right and likley damage the new motor. I have yet to see how. Or is this a way that somebody is scaming him in a service to rebuild the old carb???

The old carb was likely a Holley 4150 with either an oil pressure or vacuum governor. They are a royal PITA, and I've replaced more than one with standard 4150s and 4160s. The operator needs to restrain himself and keep the RPMs down, or the tall deck won't like the extra strain, especially in the valve train.

Holley Carbs are a real pain to set up.You changer one part in a Holley Carb,you change everything.You might want to look into an Edelbrock and throw that Holley away.The Edelbrock is much easier to set up out of the box.That is what my father did with a 1937 Pontiac street rod,had holley on it with a 350 Chevy.The car sat in a guys car collection for 10 years.He threw that carb away and put on an Edelbrock on,ran like a champ with simple adjustments.Holley carbs are not good street carbs,they are only good for racing purposes only.