That's what happened to me... cept the seller lied to me... said he was looking for 4100... I nearly walked away, but asked him what he had done... said new 465 tranny (was a TH350 I think is 86, right?) and the motor only had like 20k miles on it... the truck only have 48k original miles, and it looked like there was no rust anywhere on the truck.... We are in Wisconsin, so this is starting to look like a nice truck considering where we are, and I tell the guy I'm interested, but that 4100 is too much.
I get my wife there to look at it, the guy fires it up for us, and I drive it with the PO following with his wife in his car, to my mechanic for an inspection. As soon as they lifted the truck, I realized what I had... A rusting chassis and frame, thought the body was still straight... good tread on the rubber, good leaf springs all around, but the bottom looked a bit iffy... like it was ready to fall out. The tailgate had been replaced with a manual crank because the electric motor went out, everything was painted Fire Engine Red, and the whole truck had brand new carpet in it... On top of it all, it was a 327 rather than the pos 305 the VIN number said it had... so I had to believe the guy on the 20k on the motor. After looking over everything, the shop guys said they wouldn't pay more than 2500 for it.
I walked out of the shop to talk to the PO and said I'd be willing to pay him 2000, and he said no way... I said 2500, and he said no... I said 2700, and he said no again, and then I told him that I would be happy to pay for the gas for the trip to the shop. After explaining all the work I'd have to do (without even knowing yet about the fully bondo'd floor bed) and that said work would cost me in parts alone at least 1500, he agreed the same night to the 2700... I drove back to his house, gave him 200, and he wrote a contract for the sale. I brought the 2500 the next day and drove it away. The "as is" on the contract should have been a dead giveaway...
Then the problems started. I immediately towed 2 tons of rock from Milwaukee to my house, which is about 60 miles... While driving, I started hearing strange noises like there were rocks in the wheels (I don't have hubcaps... ) Finally, I got off the highway, slowed down, and the truck stopped without the brakes... Odd I thought, that shouldn't happen... I got the rock home, dropped off the trailer, and went to the station. The guys told me the rear end was ripped apart worse than they'd ever seen one due to the driveshaft nut coming lose inside the diff and getting caught on the spider gears... it completely ripped them apart.
Now, after the rear end, engine, clutch, radiator, carb, and soon the new metal I'm getting for the bed, I'll have over $10,000 invested in this truck... and all I wanted was a DD for $2700...
(The front light conversion comes to mind! lol) 
--I had a 600 series ford tractor with a wagner loader made of pipes!--it worked good,but had no down pressure,and it was a "trip" bucket converted to hydraulic...I still kick myself for selling it,I got it to help build my garage,after all the work and landscaping was done,and I had replaced 1 rim and tire for 400 bucks,and it sat for a year or so,I figured I'd better sell it before it went south from sitting...got 2500 bucks for it,paid 1800...I wish I had it now,it would be handy to pick the cab and bed off the truck I'm scrapping now--had to do it the hard way..cant find anything with a bucket that runs for 3 grand now.. 
