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What you really want to do in broad terms is take your time and be meticulous in your tests and diagnostics. Get yourself a copy reprint of the Ford Shop manual. About 60 bucks, worth every penny. Maybe a good old school Motors Repair manual from about 1960 say.

Start from the beginning and check everything. A lot of "golden screwdrivers" have likely been applied to your truck over the years. About half of your tasks will often be simply making right what somebody else ****ed up, or neglected. Another wise thing to do is verify true TDC on the balancer with a piston stop. This "0" point is the basis for everything that follows in terms of ignition timing and valve timing. What you're trying to do generally is get a good accurate baseline for everything, and eliminate or isolate real problems or defects versus just guessing.

Check for stupid stuff too, you'd be amazed how often spark plug wires are mixed up, happens more often than you'd think. It doesn't cost anything to check stuff other than your time.

First test in any manual on pg. 1 is always the Cylinder Compression Test. This checks out the internal condition of piston compression rings and valve action etc etc. It's the very first test in the books because, it's not worth spending time or money on a tune-up if the engine is completely wore out or has major defects. If it passes the compression check OK then the engine is a good candidate for a tune-up and some upgrade goodies.

If the engine checks out OK compression wise I would start with the electrical system and ignition first, to include fresh battery cables, ground cables, and connections, of adequate gauge size. No drugstore battery cables, get good ones. Good fresh high ampere battery, and check out the charging system thorougly, make sure it's at 100%; oftentimes ignition system faults are mistaken as carburetor problems.

A carb will definitely benefit from cleaning but they pretty much will work OK so long as nobody has buggered it. Get in the manual and study it, when you get everything else squared away the carb is ready for fine or at least final tuning. Take each major system one at a time, study the manual and focus on it. The fuel system starts all the way back with the tank, old skudge and varnish will cause nothing but trouble. Make sure the fuel pump has the right output, not too high, not too low. Fuel lines not clogged. If you do this stuff I guarantee it will come around and eventually you'll think it's a new engine. Plus, you'll thank yourself everytime you drive it, and you'll gain the satisfaction of having done it yourself.

I don't think anybody is here to argue with you, there are accepted maintenance practices that go back 100 years. They hashed all this stuff out a long time ago. Pg. 1, Para 1 in practically every repair manual ever published is Compression Test. You want to get a baseline for your "new" engine. When you start getting things squared away you will see compression figures improve.

There are other ways of doing the same thing. A vacuum gauge is one of them. While it doesn't replace a compression test, engine compression can be directly inferred through manifold vacuum testing. The idea here is to go about your troubleshooting in a methodical, straightforward way. None of us are there working with you, all we can go by is what you report. Try grounding out plug wires one at a time at idle and see if the RPM drops or not as suggested.

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Look on that auction site. Good used Snap-On combo sets - timing light, vacuum gauge, compression gauge. Maybe 50 bucks. All kinds of stuff there for decent prices. I found a new compression gauge for under $20, quality not too bad. Good enough.