I'm thinking the same thing as doubledingo. Even here in the land of rust, I would offer $2k, MAYBE $2500 if the thing was really that rust free and ran great. The guy left it parked in the weeds with a smashed in door, if it is such a great truck why isn't he driving it around himself? Interior is decent enough, but it obviously needs a good deep cleaning and the exterior needs a little body work and paint all around. Plus, after sitting so long I would think everything needs to be gone through (brakes, fluids, tune up, de-mousing, etc). If I were the guy selling it I'd at least take a shop-vac to the interior, park it on gravel and hit it with the hose... leaving it in the grass just says "I don't really care about this junk".
These trucks are older and becoming more desirable especially shortbeds, but let's all stop pretending like these things aren't still everywhere you look. Hell, in my town of under 5k people up in rusty new england I can think of almost 20 of them off the top of my head, some rusty piles in yards and some are shiny jacked up beauties. Just because they're getting older does not make them "rare", especially not a truck with square lights, it's not even 4x4. I'm not saying the guy is ripping you off, a decent truck is worth what it's worth, but don't overpay for a 40 year old truck that's been left sitting in the weeds with rust and dents, don't be afraid to offer what it's worth and haggle from there. If you offer $500 the guy will tell you to go kick rocks, but even if he was asking $3k, 2 is not an offensive offer, especially since you already said he's asking under $3k. Obviously he can counter somewhere closer to 3 and you can work him down to 25 or 22, maybe less depending on what it needs. He might be reasonable, who knows?
Whenever I buy a used vehicle, especially an older one, as long as the thing is not too far gone I say be prepared to pay full price and try to get it as low as you can from there. If what he's asking doesn't immediately turn you off, then show up with a trailer and cash (maybe a hundred or two less than he's asking so worst case scenario you can say "look man this is all I have, take it or leave it"). I never talk price before I get there, put him on the spot. If he wants to sell it and you're standing there in front of him with a trailer and a *** of cash, he'd have to be real stubborn to tell you to leave over a few hundred. If you see selling a car for $4k and your initial reaction is "hell no way would I pay that much, 2k max" then don't waste your time he probably won't come down enough to make it worth your while. But if he's asking $27-2800 ish and you think you can live with it, then hey worst case you still only paid a little more than you wanted. Stick with your gut, and hey you might as well try to save yourself a few bucks while you're there, can't hurt anything to ask for a better deal especially if it needs work and isn't already a steal...
Either way, looks like a decent truck to start with, hell I would probably even drive it just like that for the time being and not worry about it. I hope you get it. Welcome aboard!
