1978 f250 351m carburator
If you buy a rebuild kit for it, there will be a couple of pages included. One is instructions and specifications, like float height and choke settings, that kind of thing. Another page will have an exploded view of every part or piece, and they are numbered. You follow the numerical sequence when disassembling it . It keeps you from running into trouble. Keep things organized, so you don't get jets or parts mixed up. Use trays with several sections, or little cups, or even a few egg cartons with numbers on each little section. There are a lot of parts- anywhere from about 80 to over 100.
So you get it all apart and clean everything, including all the internal passages in the carb body. People used to use a strong dip available that you could just drop parts into, especially the larger parts that had those passages, and it cleaned them ferociously. I have been told to not even bother with it anymore-environmental regulations have made it rather weak. So just buy one or two cans of carb cleaner and spray everything. Use the little tubes that come with the aerosol cans to hit all the passages.
If you need anymore, you could buy a Haynes or Chilton repair manual for your truck. Lots of information on the carburetors in them. I like the old cars and trucks, still own a carbureted Sentra, but I like fuel injection systems more-nowhere near as many parts to contend with. Good luck.