The high idle might be a vacuum leak somewhere, not necessarily the carburetor.
It also might be (no offense meant) installing the throttle plate in the carburetor upside down.
Check the throttle positioner screw to make sure it is not making contact, and the fast idle (if present) linkage is correctly adjusted.
Regardless of what some might have you believe, you MUST have some clearance with the throttle shaft to throttle body. Design clearance was 0.004~0.006 inch. An additional wear of 0.003 inch is acceptable. Measure the clearance with a dial indicator. If it does not exceed 0.009 inch, no problem.
Lots of black smoke could be either ignition or carburetion (come to think of it, the high idle might be a faulty pertronix conversion, if you have one).
For the black smoke, you should test for fuel pressure at the carburetor (less than 5 psi). Did you test the float while you had the carburetor apart? You also need a compression test on the engine, and a firing voltage test.
Run some tests, you will figure it out.
Jon.
