It is running rich. How do I adjust the carb?

Running rich is a term to describe the fuel to air ratio as being to " rich" with fuel and simply means you need more air.
Usually done by adjusting the carb.

Well the correct way of doing it would be with a 4 gas analyzer but without that you would have to use a vac gauge.
Once you get it running and have the timing set, the carbs would be adjusted lean until the RPM and vac drops, then go rich a turn or so on the adjusting screws. Most Holley carbs start at one or two turns out.

you should be able to adjust the idle screw a quarter turn at a time until it runs

either the float is sticking, when it is running use the back of a screwdriver and rap the bowl and see if this helps, or the jets need adjusted, start with the right one first, turn in untill the motor starts to lag then open it up untill the rpm stops climbing, do the same with the left one also, see if this helps. let me know.

downdraught or sidedraught ,if downdraught then you will need a new main jet ,have you checked the air filter is clean ?'

You may have an internal carb gasket leak or your floats may be adjusted too high.After you run the truck look into the carb to see if there is gas still dripping into the carb bore.Also after running with engine on remove the front fuel level check screw. (have lots of rags under to catch fuel) Fuel level should be right below hole.If it is spilling out it is too high.Floats need to be adjusted up for fuel level to go down.

float is not adjusted right or pressure regulator is bad. berrydalewolf

use the air and gas flow adjustments on the side of the carburator to adjust the rich/lean flow of gas. there is a srew on each side of the carb to adjust one is for air the other for fuel. the one on the driversside is for the fuel and the one on the passenger side is for air. you have to turn them slowly til you get the desired results

There are only sealed adjustments for idle mixture usually, is it running too rich at all times? might need the carb rebuilt

There could be all kinds of reasons your vehicle runs rich. It should be fuel injected not carborated. It could have a bad injector, bad air filter, o2 sensors etc. Have it scaned for the reason.