Once the engine RPM gets above 1000 or so, the idle circuit completely ceases to function, so you can tinker with the idle mixture screw until you wear out the threads and it won't make any difference at all on a sooty tailpipe. The proper way to adjust idle mixture is to turn the needle clockwise until the intake manifold vacuum starts to drop (too lean), back it out slowly to get good vacuum, and go about 1/8 turn richer (CCW) to avoid a stumble on acceleration. Then use the idle speed screw on the throttle shaft to set your desired idle speed.

THEN LEAVE THE COTTON-PICKIN' ADJUSTMENTS ALONE! They're for adjusting idle- - - -nothing else!

The high speed system consists of the main jet, the venturi, the float level, and the power valve, and on virtually all carburetors, the only "adjustment" that can be done is changing parts. A VERY few carbs have adjustable main jets, and none of them say "Rochester" anywhere on the casting- - - -most say "Zenith" which is a contraction of "EXPENSIVE". To run a 216 carbuteror on a 235, someone would have to file slots in the throttle body mounting holes (I gave one like that away last week), or install a 216 intaqke/exhaust manifold on a 235. Either way, the increased airflow through the carburetor will cause the venturi and main jet to run the mixture too rich at any speed above idle. That's why the new "one size fits none" copies of old carbs made in third world sweatshops by teenaged slave laborers don't work.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!