Regarding common problems:

Usually the front axle seals are worn out. The front knuckles should be relatively free of grease on the outside. The bearings usually need repacking. Check to see if the front bearings are loose by wiggling the front wheels top to bottom.

The front axle on early trucks is not as tough as some people think, and it can be bent leading to a pull in the steering. Later axle housings have a gusset to address this problem.

Usually the clutch pedal has to go all the way to the floor to work. The clutch master cylinder usually needs replacing or at least adjustment.

Oil leaks at head gasket is pretty common.

Warped exhaust manifold is common. Also heat shield between manifold and block is weak and can crack, leading to an exhaust leak. This part is NLA.

Damaged exhaust threads in the block is common. Make sure exhaust pipe is supported at the block near the oil pan.

Overheating is pretty common, and can typically be traced to a bad radiator. You might find pinhole leaks in the water pump housing.

The 22R engines need timing chain replacements at around 100K.

Rust in the frame and elsewhere is common.

Input shaft bearing on five speeds is a common problem.

Gas gauge malfunction is common.

Destroyed dash pad is common. Interior parts are pretty much unavailable.

Doug
80 4x4 Truck