They have surprisingly few true Achilles' heels that result from poor engineering. It's not like those ZF or Ford transmissions which are effectively guaranteed to fail no matter what you do. Most of these things that went to the junkyard were the result of owner neglect not a shortcoming in the machine.
The OE alarm is often a pain in the neck but if you have any business at all owning an old car you'll be competent at wiring and it is trivially easy to bypass it or install a new remote (recommend Avital 3100 it's reliable, simple and affordable) . The circuit on which that starter interrupt/alarm/remote exists is analog and easy to trace.
For some reason a lot of people struggle with the coolant system on these things. It's possible you will need to replace the radiator or have yours re-cored if somebody didn't do a good job with that, is running hose water instead of distilled, etc. - the heater core is unfortunately a huge pain in the neck to replace and there are no shortcuts on it (many have tried..) - so if you get sweet coolant smells in the cabin you got some work ahead of you. For many people that's the actual worst job there is to do on these vehicles. I'd rather remove the engine than replace the heater core, in terms of how much work it is.
The valve guide seals age and that leads to oil consumption and failed catalytic converters and poor mpg as a result of the oil caking up inside the exhaust system and oxygen sensors. Running heavier weight oil will not fix this and may make it worse. The only way to actually fix it is replace the valve guide seals and run the specified 10w30 oil. If you need to buy some time before digging into the seals you can try to clean some of the varnish and gack off the old seals to help them seal a little better by giving it a fresh oil change & replacing one quart of oil with Marvel. This will thin the oil out a little (like.. 5w25...) and dislodge just about any crusty crap that's in contact with the oil and mobilize it to the pan or the filter. Your next drain will probably be gross if it's been neglected in there but subsequent intervals will be considerably
less gross. Like I said if you have leaky valve guide seals this may buy you some time by removing the crust around the seals & those little springs that hold them tight, but ultimately if the seals have not been done they need to be done and that's probably the 2nd hardest job on these vehicles.
The steering kingpin bushings wear out with age, well all of the steering linkages wear out ultimately. These trucks handle very tight and nimble when you have it all dialed in so if the steering is at all sloppy or vague there's something worn out down there. Most of it is easy to replace.
The front axle disconnect is vacuum actuated like most vehicles which have 4wd and spindles... and like most vehicles of that sort the vacuum hoses are rubber and two decades plus an oil leak above them can destroy them. The solenoids can fail, the actuator diaphragm can fail (though it rarely does).. when it fails all the way that just leaves your front axle locked in like as if you were in AWD but you don't want to drive around in 2wd at highway speeds like that because the front ring and pinion will be running on the back side of the gear teeth and this generates significant heat, damaging the oil and seals and the plastic breather nip. When the vacuum bits fail partially it leads to a "grinding gears" sound while you drive, which is the sound of your disconnect clutch and the bearings in your front axle being transformed into glitter. It is no bueno. You want to fix that. It is easy and cheap to fix properly if you get it early.