I was given a free aluminum cap today, the old guy that had it swears it came off an older F150 but can't remember what year. The foot print of the cap measures 77" wide by 99.5" long.

I own several trucks, all 8' beds. I've got a 1959, a 1972, a 1977, and a 1986, plus I've got a 1979 Chevy C10 sitting here. This cap hangs over the bed rails on each side by almost 3" on both sides. The inner edge of the cap where you would bolt it down is way too wide for any of these. Its also a tad short to fit right on any of these, the front flange of the cap just barely catches the front bed rail with the back door closed.

Any idea what truck had a 77x99.5" bed size?