I dunno the specifics of your truck, but I do know that on my 89 turbo voyager the wiring for the computer passed near to teh battery and all it would take is one good acid spill or boil over and the wiring would corrode showing all sorts of weird symptoms.

I would start with a good charge and load test on your battery. It might be flaking out on you , I've seen that cause funky symptoms too.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.