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?

 

No clue but i think I have one of those in the back pasture, aluminum with windows all the way around. Would be cool if it fit, but it doesn't on my 79

 

So far every truck bed I've measured including a half dozen utility bodies, are too short or way too long, and the width is just wide enough to slide down over the bed sides of every truck I've measured. Its also too narrow to fit atop any of the utility bodies I've seen. Besides, who would put a camper insert with paneling inside on top of a utility body?
Pretty much all the Ford 8' beds I've seen have had the same basic length, even the newer trucks, and I've not yet seen one with a bed this wide. The guy that had it swears it was on an F150, but has no clue as to what year it was. The only thing I've seen it matches so far is the top of an old popup camper I've got here. It matches its outer dimensions exactly.
This cap is heavy, about 400 lbs or more. It takes four guys to move it. Its built mostly with wood inside but has an aluminum frame. The way its built makes me think its in the 70's, most of these from the 60's were all wood with just an aluminum skin, but that's only a guess.

 

the lenth is right for an 08 f-350 bu the width is way off. maybe this is from a 450/550 size truck.

 

I thought about that but this thing is from the 70's.
I think the length on all Ford long beds stayed the same, the cap off my 1980 will sit on the bed of my 2007 just fine, it just don't match the cab height.

This aluminum cap is aluminum over wood, so that makes me think its got to be for something older. The guy I got it from swore up and down it was off his Ford pickup but he had no clue what year it was. Either way, even if it were way older, this is way too wide.