If it has that much paint on it, i'd get it to factory prime at least. You probably read my post on paint thickness, mils, etc and potential failures...
the 3 trains of thought for stripping are mechanical, chemical and mediablasting...
generally these days, I go mechanical for a strip job. mainly because i'm lazy. Plus you can control at what layer you stop easier than a stripper.. With a highend DA paper like 3M gold in a burly 60 grit, you can do some real damage.. you can generally strip a blazer in 1/2 a day depending on whats on it..
Some folks prefer a chemical stripper... Couple things to be aware of tho... Tho i've never had a prob with it, removing all residue has been an issue for some with later topcoat failures... I've always found that if neutralized properly, it's not an issue.. You have to DA it thoroughly after anyway, so that also helps avoid these issues unless your DAing stripper "into" the metal..
another prob with stripper is it CAN take longer in the end, not always but sometimes. By the time you carefully apply to avoid rubber, plastic, etc, then wait, then scrape, maybe reapply, scrape, neutralize, and sand, you could have stripped it twice with a DA. One advantage is less dust, but you make up for it with piles of goo.
Another point to be made about strippers is, depending on what coatings are on the truck, sometimes it'll only go down so far thru the layers.. On many occasions I've seen it tear up factory paint and not touch the underlying primer. thus, more sanding... THE best stripper I've ever seen bar none, is Aircraft Stripper brand. square gallon containers, and all the obvious safety precautions should be taken, gloves, etc...
And obviously you have media blasting, from walnut shells to plastic media, etc... and I'm sure you can imagine the issues there... A much better option when the truck is disassembled..
Back in the day of restoing cars and trucks, alot of the time we would stripper it and scrape thoroughly, take a power washer to it, then come in the next day and DA the heck out of it... You really need to get all gooey paint off with the washer tho, that stuff will stay soft for days and immediately clog DA paper if you hit it... It was probably easier than DAing it all off, but like i said, I'm lazy these days...
If you do decide to go with a straight mechanical, which is what i would suggest so you can determine how the different layers are and how deep you want to go, i can't emphasize how much quicker it'll go with a quality paper and a DA that can keep up.. We've found that that 60 gold cuts way faster than even a gnarlier 36 grit. then obviously you need to run over that bare steel or factory primer with some 180 to 220 to bring the scratches up to a reasonable grit for priming...
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