I have a Holley 3310-3 which is a 750 cfm carb on the Willys. The motor is an Edelbrock rpm 350 with the rpm air gap intake.

After a bit a swapping shooters and pump cams it runs great. We are working with the vac secondary now. We can get it to sort of lay down or run out of air by not opening with the stiff spring. By changing the secondary springs in steps we have it so you can't really feel the secondary come on. Actually if you feel them you are experiencing a bog then a surge. It helps to have ear plugs so you don't equate the carb noise with additional power. This is a great carb for almost any normal engine...if there is such a thing. I had the early version 3310 on my 395 375 hp Chevelle and it worked great back then too.

The next step will be some fine tuning to get the A/F ration exact. Not going to worry about that untill spring however.