1976 Cadillac Eldorado (Carbureted engine)

Have had subject car since new. Currently 28000 mi.
Carburetor was rebuilt about 2 yrs ago with NAPA kit.
Onlly about 1000 mi. since rebuild. Engine starts and runs OK, but I believe it is running grossly rich. When parked at idle a sooty patch is deposited at the tiailpipe in a short period of time ... 5 to 10 min. Fuel milage is atrocious...OK, I realize it never was very good, but WOW!
I can't detect any significant performance problem when accelerating or cruising.

Any ideas?

Thanks,

Bob