Help - Unsafe or Rock it?

Looking around found a few listings stating its 9'6" but many more of an 1989 LC580 at 10'6". IF it were a 10'-6 thats 30" overhang on a 8' bed.
Yes DO check cab height

The LC-580 is a 10.6ft truck camper..I have the LC-480 tagged by lance as a 2660# camper and weighed appears to be spot on..My point is my DRW F-350 has 4600# of manufacturer rated payload and I am within a couple hundred pounds of being maxed out on GVWR on an F-350 longbed ready to camp...6K on the rear axle for my 9.6 on a longbed,you would be more for my TC on your truck because it is a shortbed..The 10.6..More than that.

If you had a longbed,I would say go for it as Specta does the same with a 11.3 TC on a 3/4 Chevy longbed in the same erra as yours.. I have seen 3500 series(1-ton) trucks with longbed Truck Campers(8.6ft) on shortbed trucks without any issues but never a TC as long as that one(10.6) on a shortbed...

Might wanna load it up and see how it fits and take it for a short drive empty to see how it handles first..That's what I would do on that TC.

Also, check the cab over height if it clears the truck cab. Many older campers may not fit the taller cab or bed height of the new trucks.

How long is the camper and how much it weights?

Twenty-one inches short on a thirty-one year old TC? You should be concerned with COG and drop this idea.

Leaving the tailgate down won’t help much. I suppose I’d try the camper assuming it’s 8 1/2 and avoid putting weight in the back of the TC or at least put heavy items in front of your axle.

The bigger concern is your tires to make sure your tire payload capacity is enough.