Carlo,
Don't get me wrong about the carb shop, what that fella knows is a wealth of info. However, he absolutely will not sell jets separate from a kit and will not sell you a kit that doesn't match your carb #.
This is my first suggestion to your situation, take the two carbs apart and do a little notetaking. Make sure your two venturi bodies are the same diameter: take off the top of the carb (called the air horn in the manuals) and measure the top of the venturi. Next, take the cast iron butterfly body off and measure the butterfly opening. This butterfly housing should have a 3 digit number casted into it and I've only seen two variations. There is a spacer between the venturi housing and the butterfly housing, compare these closely. After you've measured and compared the butterfly housings compare the venturi housings closely by measuring the top and bottom ends, take out the aluminum plug and remove the brass acclerator jet, and reach through the accelerator hole with a drill bit to compare the opening for the venturi fuel port. Measure the fuel port with by inserting different sized bits like a go/no go guage. By the way, you are going to need every size bit you can borrow or buy to measure and standardize the carbs.
As long as your housings are the same dimentions in venturi, spacer, butterfly housing - you are in pretty good shape. One absolutely necessary set of bits to have are the ones used by heating and cooling technicians used for re-sizing orifices. These bits go from .010 to .125". Not only will these bits help you to understand what you have, they will be needed to standardize your carb as I have never seen two different #s have all the same orifice diameters in either the housings or jets. Each # was produced for different applications and cid used for that particular contract.
Take a drill bit set and the orifice drills and measure each jet, air bleed, and vacuum port. Trace all your vaccum porting to make sure they are alike. The only external difference that could cause problems is the length of the throttle arm that the cross linkage attaches to for the dual setup. It sounds like most of the external mechanicals on your setup have already been addressed.
The most important thing here is internal standardization, then let the tuning proceed from there. You need to invest in or borrow a good synchronization gauge to properly get the carbs working together.
Our engine seemed to run fine until we called on it at the track, proper tuning of the carbs is just as responsible for the rpms and revving as the engines ability to withstand it. Now that we've got the tuning on the carbs right, the engine seems altogether different - in a good way.
Hudson
