You will probably get more of a benefit from advancing the ignition timing at idle a little, rather than messing around with swapping carburetors. Just one problem- - - -for every degree you add to the base timing, you'll need to subtract a degree from the centrifugal advance. That's done by limiting the distance the advance weights are able to travel- - - -NOT by installing stiffer springs. Drop me a PM and I'll be glad to walk you through how to modify the distributor by email and/or telephone. The procedure is a bit complicated to describe with a keyboard. On engines with enough of a cam to give a lumpy idle, I've found that around 15 degrees of initial advance or a little more is usually necessary for good off-idle performance. That also makes a noticeable increase in idle manifold vacuum.
Jerry
