I might end up doing the same thing on my 408 thay has been for sale and nobody wants. Its a W2 408 with a girdle and built to run street/strip with ported heads. I have a single 4 barrel on it now, but I am thinking of putting the holley Dominator tunnel ram on it with a pair of 600 vacuum carbs. I have the 4150 top plate for it.

My research from numerous sources keeps bringing me back to the Holley 600cfm vacuum secondary carbs. Now I want adjustability, because I want my car running 6.90's in the 1/8th on pump gas so best I have found are these from quick fuel. In my past dealings with them, they will customize to suit your needs. I do not need a choke horn or the weird vent tubes, but the adjustable air bleeds are a must along with the adjustable vacuum system....I also do not need the vacuum port at the bottom of the carbs. Just simple straight up vacuum carbs with adjustable air bleeds and vacuum spring adjustments. I als don't want somebody's old worn out junk either. These are real nice for the cash, and I think they might fit the bill if my engine does not sell. I can go nostalgic old school with a pair of these...