[vector1]

you're sure it is the carb?

no vacuum leaks?

dist. mechanical/vacuum advance working properly?

i'm thinking maybe at some time the idle circuit got gunked up and you opened the butterflies?

or, at some point did you turn the idle adj. screw and open the butterflies uncovering the transition slot which means the idle circuit can not be used to tune the idle a/f mixture? there should be only about .040 opening at the primary butterflies.

the no adjustment at idle would indicate fuel is somehow getting into the intake via the secondary circuit.

and you could have two problems here, in searching for one you've created another, or fixed one and created another.

pcv valve?