The price of these trucks are really all over the place...
I suggest making a low offer and see if he takes it. If he laughs at you say long bed ¾tons aren't that desirable and the V6 is a gas guzzling boat anchor that is hard to find parts for. It needs to be a ½ton short bed big window to bring the dollars.(I own a ¾ton longbed V6 so please don't take offense
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From there it is really a matter of how bad you want it. Paying more for a clean, rust free truck that has never been in a wreck is usually cheaper in the long run if you plan to make it really nice.I wouldn't buy it if flipping it is what you have in mind. You might get stuck with a huge repair and the profit margin isn't that big.
16.5" tires are pricey so you might need wheels if you need tires. If it hasn't been driven the tank might need replaced along with the sending unit... clutch, brakes etc....