the mofoco heads flow a hell of alot better than stock,You look at the progressive carb and the venturis are about the size of a quarter,whereas the weber are more like a half dollar the more air and gas you can get in your motor the more hp you will have the progressive is like a restrictor plate in nascar racing you can only do so much with it.Trying to jet a progressive is a pain you have to take the top of carb off because the jets are in the float bowl the 40 or 44 weber jets are all on the outside and you can change jets in a matter of minutes.

aaron