Well here goes...

1992 Corvette
$1.25 in the '92 vette. Had to take the drivers seat out to unstick the handbrake and found it.

1989 Phord Van conversion
Bought it new so you wouldn't expect anything to be in it. But found a 3/8" socket left over from the conversion.

1962 Studebacker Post Office Van
Bought it from Government auction in 1970. Converted it to a camper. In the conversion found bulk mail undelivered down between the dash, a big flat area, and the side of the van.

1959 "Bugeye" Sprite
Found it in 1974. About a hundred pounds of bondo on the back of the car.

1980's dually Military 1.5 ton panel truck.
It was the best and not even mine. My neighbor across the street, when I lived in Merritt Island, FL, used to collect and restore old military vehicles. He purchased the box truck from just outside of Washington DC, in Maryland, at one of the air bases. Drove it back to Florida. It had been abandoned at the base. As I was helping him dismember the interior, it had a desk and cabinets built in, we started finding Gov' documents that had slipped behind the cabinets. Nothing particularly important that we could make out. I seem to remember CIA on some of them. We surmised that the truck had been used for 'black ops' and abandoned at the base. My friend said that no one seemed to know where the truck came from when he picked it up.

Looked like the truck described in the book "Clear and Present Danger" that has been made into a movie. In the book the truck was used to run the op in Columbia, South America. I don't remember seeing it in the movie though.

That's about it for the moment. Still looking for a 40's - 50's bolt.

Great thread, Wade in Florida