Truck will crank and then shut off

loose connection on the fuel pump, or the fuel pump is going out. either way its dropping the tanks and checking. Good Luck Tim

sounds like you need to bump the timming just a hair. loosen the distributor bolt and turn the whole shaft to the left if that doesnt work go the other way

Possible things to be considered: Float level too high, needle has a bad seat and won't shut off, vacuum leak (either internal or base gasket), choke not properly adjusted.

My money would go on a carb. rebuild kit (but only if you feel comfortable attempting it) it's not all that difficult, but you MUST be (1) an absolute nut about cleaning it all very well, and (2) the various gaps, clearances, adjustments, must be made with excruciating precision.

This will be a lot cheaper than a rebuilt carb., and you'll get the satisfaction of doing it yourself.

While you're at it do a general tune up.....plugs, points condenser, wires , air filter, PCV, etc.

is float stuck. does it run good.if it leaking under carb. it got to be flooding.

In general, yes. This is a carb tuning issue. Another possibility is a vacuum leak somewhere, but most likely, it's a carb issue. You'll typically see your rpm drop a bit when you put it in gear, but that it sometimes stalls out points to a carb issue.

does the engine turn over?

your truck is a 4.9L, make sure you have power to the front tank fuel pump. is the power to the pump is ok and you can hear the pump run for a second or two when you key the vehicle on... replace the fuel tank selector valve

sounds almost like the newer vehicles equiped with cam sensors instead of the distributer system i had a similar problem with an 87 ford bronco 2 it would stall out right around 2800 rpm i replaced the control module usually mounted on the distributer at least mine was and it fixed it right up but as for ur truck im not sure they are only like 30 bucks at autozone or something worth a try right??

run a fuel injector cleaner?

carburated or fi?

you might wanna try to clean/rebuild the carb