Depending on how bad the carb is, just a spray of carb cleaner while it's running will get the gunk out of the venturis and hopefully clean up the air bleeds(where it draws air in on the sides). This sometimes helps a bit.
If the carb is in real bad shape, then disassembly and a real rebuild is in order.
Setting the idle mixture screws is relatively simple. Usually turn them in til they just bottom out(just touching). Then turn out 1 1/2 turns and start truck. Get it warmed up and idling smoothly. SLowly turn each one in til you hear the motor start to slow down. Go back out 1/4 turn. Do each screw separately.
In the end, both should be out the same amount of turns(roughly within 1/4-1/2 turn). You can use a vacuum guage to get more accurate and adjust for the most vacuum(which would be the highest idle speed). But in a pinch, listening will work.
As it's running, manually rev it up a bit and spray it right at the venturis(the holes in the middle). Usually once the cleaner gets into the engine it will falter so don't over do it. Give it a good shot and let motor come back up then repeat. You'll see what I mean.
Keep spraying around and you'll see the junk start to wash off. Likely you won't notice any great affects, but depends on condition.
I fix and trade in a lot of gas powered things. Anything that has not been ran in a while, and especially if it was parked outside, needs the carb disassembled and cleaned. I find a lot of small engines have the needle varnished into the seat. Generally just a good sprat cleaner, I prefer Berryman's B12, sprayed through all the passages and blown down with air, and clean the obvious crud, put it back together and good to go. I don't even bother with a kit unless the gaskets are toast.
I also always run in any adjusting screws and count the number of turns, then remove so the passage can be blown out.
If it's time you really want to learn something about these & your classic it's time to buy a manual so you'll have most of the answers right at hand. If your out on the road and it breaks down on you, you'll be more apt to get her going and Home with out a tow truck..A fairly good one is Ford Pick-Ups & Bronco many online stores sell them also..
Manuals are good. I find any but the factory ones lacking. Don't even bother bringing home a Haynes from the parts store.
Aw manuals are like women, they all have some little thing different about them. But enough info for the novices to get by who don't want to spring for a Ford truck shop manual tho.. my 2cents...