Before you adjust your linkage back off the idle speed (Not mixture) screws so they are not making contact with the cam.
Then, slowly screw them in until they JUST make contact, then turn both of them exactly the same amount, about 3/4 turn. This will give you a base idle but more importantly you will know that both carb throttle plates are open equally so each carb is flowing the same amount of air. Then hook up your linkage.
When it's running, whenever you adjust one idle speed screw you must screw the other in or out the same amount, this will keep the carbs synchronized so you get equal flow to each cylinder.
and ensure that one carb is not doing more work.
Another thing I forgot to mention about Langdon's C/W kits is that the stainless socket head bolts he supplies to mount the carbs to the adapters are too small of a diameter. They don't "square up" the carbs on the spacer, they allow too much fore/aft and side to side movement, not ensuring that the carbs are exactly centered over the adapter bore and gasket. When I got my truck one of the carbs was offset towards the valve cover and the other was offset towards the driver's side. When I took the carbs off I could see in the imprint on the gasket that the oval hole in the gasket didn't correspond to the throttle bores.
Get yourself some stainless 5/16 by 1 and 1/4 long bolts, washers and nuts. They fit through the carb base holes snugly as well as the slotted holes in the adapter. There is still a little play in the adapter holes so just eyeball it closely and center both carbs equally.
I hope it turns out well for you.
