I'm with the majority here. In Michigan, it's hard to find a 400 that's not all rotted or clapped out with less than 120k miles, let alone find one for a decent price. I've always tried to find vehicles based on mileage and cleanliness of the body. I can do a lot of mechanical work, but I know precisely nothing about body work, and that gets expensive having it done...
Since we're in the same state I figure I'll throw my criteria in here as well.
I do not really care about mileage other than I kind of prefer high mileage as that kills the value for most people, so that's a plus to me. (especially if I don't plan to resell it. If resale is your goal, low mileage ought to be too.) Although I will say of the GMT400's I've checked out, 200-230k on the original engine seems to be about all they're good for unless you know the complete history. Either the cooling system gets neglected and they run it hot, or they run it empty on oil..
Speaking of the odometer, take a good look at it. I can't recall the amount of GMT400's I've seen with pictures of odometers which display blatently obvious odometer fraud (some gray/silver bars showing between the digits). It's not even hard to change the odometer's reading such that the black bars between digits remain. I've had to do it when doing the moonie to needle swap. If you see that, might as well not even bother calling unless you want to subject your ears to vomit like this: "Huh, what are you talking about? That's original mileage. Stop wasting my time. It's a 30 year old truck." blah blah f'in blah..
Unless you're trying to buy a shell or a vehicle for body/interior bits, or you don't value your time spent wrenching or don't mind going over budget, never buy one that doesn't run. Because even a vehicle that runs & drives poorly can still tell you what else you might be in for. Like worn u-joints, ball joints, tire balance issues, worn synchros/dead gears/bad transmission, bad rear end, driveline vibrations, dead cylinders, rod knock, valve train noise, oil consumption issues, brake issues ect ect. Get the engine good an hot when you test drive it, even if it takes 20 minutes. If the oil pressure is 15 or less when hot at idle, consider walking.
Then there is rust. In Michigan and other salty areas we don't have much of a choice. Sometimes people list clean stuff with no idea, so the price isn't inflated to reflect it. It seems like big business around here as many people list stuff as "Clean Georgia Car" or "From out west." Depending where the rust is and how bad it is, I'll gamble on it. Especially if I'm going to subject the car to salt & moisture. People don't realize that a coating system has a life span, and even though the truck/car may not have seen any salt in it's life, that doesn't mean it'll stay rust free for six years or more like it would have when new. Nope, take it from me, your humble advisor who works in the anti corrosive coatings industry. You'll get maybe three years before you see corrosion. And if you see it on the outside, it's 3x worse where you can't see it. Sometimes some vehicle fare better. My truck for example, the rockers are ~50% gone on both sides, cab corners jumped ship a long time ago and the wheel lips are crusty. However, when I looked at it I noticed the frame was still clean and the floor pans, fuel & brake lines weren't rusty so I popped on it. I've been treating it with Krown T40 every year and the only things getting worse are those wheel lips, which will always go anyway due to the nature of the area. But if the car in question is worse than, pass. You'll always end up chasing your tail with something like that. From electrical diagnosis to brake & suspension issues to water seepage. Just not worth it unless you're a *********, maybe.
