Not trying to bust on the self appointed wizard who taking your money, but he doesn't seem to undertstand the basic operation of carbs. Then again, a lot of guy who can sling around an impressive column of numbers don't understand basic engine operation.

The cfm and jetting are 2 differnt puppies. Cfm is the cubic feet of air per minute that can enter the venturie(s). The cfm of the carb and the engine must match. When you overcarb an engine, meaing using a carburator that has a higher cfm than the engine can use, it decreases the velocity in which the air/fuel mixture enteres the engine. The velocity "injects" the fuel in the engine, the stronger the velocity, the more power the engine has. I don't know where the point is where a 350 sucks enough air so that it can use over 650 cfm, but I don't think that the current configuration is in that area.

Jetting relates to air/fuel mixture. It's not that jetting doesn't have anything to do with cfm. Yes, cfm makes a difference on jetting. But you cannot reduce the cfm (in this case, the reduced cfm increases engine velocity) by reducing the jet size.

Something tells me that the guy has vested interest, such as more money in his pocketbood, by suggesting an oversized carb.

I know zip about holley's, but don't they make a 650 cfm holley? If you're bound and determined to use a holley, use the 650 cfm if such a puppy exists.