Found quite a bit of stuff in my 72 when I bought it the interior and trunk was so full of stuff you couldn't see the rug or trunk floor.
List of my finds
$15 worth of change
All the original owners manuals and associated papers in the glovebox
The paper work for the replacement engine, stereo install from '89
Receipt warranty papers for tires from '89 along with the along with the check from them. These tires were still on when I bought it.
Original key tags in the mini console
Ashtrays were packed with ashes and candy wrappers front and rear.
The original oil breather and hose in the back seat
Receipts for gas for $1.98 gallon and tons of candy wrappers and some hairpins
Various clothing like jackets, a hat and some shirts
Bottles of oil and the oil change pan full of dirty oil sitting on the front seats
Now for the trunk
Spare tire and jack, also the spare tire cover and trunk mat
A bible and some school books
Socks, golf tees, golf balls, and some more wrappers and garbage
A new starter in the box
A set of felpro new in the box oil pan gaskets
Old set of antique plates last registered in '91
Various bottles of wax leaking and dried out
Key for the wheel locks
A chiltons manual for mustangs
And some various broken plastic pieces for the interior which I glued back together
Other interesting finds in junkyards were
71 convertible with $25 worth of change in quarters
74 cougar with nos parts in the trunk in ford boxes
74 mark 4 with trunk had rope, shovels, various hand tools, photos of random women in an envelope, and some interesting "manuals" and "books" lets just say I closed the trunk and didn't take anything from the car.