Measure the tailgate width opening of the truck and compare to the rear width of the camper where it fits through the tailgate opening. Older trucks of that camper's era had ~65" tailgate opening. Newer trucks have ~60" tailgate opening. Additionally, very late model GM trucks have even less than 60" at the bottom corners of the tailgate opening.
The tailgate opening width is the only fitment problem that is a big bear to get around. The other issues, such as cab roof height and bed rail height, are easy to fix by spacing the camper up in the bed with a platform on the bed floor.
All you can do is try it, CAREFULLY. Be prepared to take a couple of hours as you back under the first time to make sure that everything fits properly. Lower slowly and carefully checking everywhere as you go just so you don't drop the cabover section on the roof of your truck.
2002 Chevy 3500 DRW 8.1L/Allison
2000 Palomino B1500
...and the reason why I need a DRW to haul a Palomino:
2004 United 7x14 tandem axle enclosed toy trailer
2011 PJ 8x20 7-ton deckover equipment trailer
It's hard to say when they started building campers to the 60" spec, but I would guess it's sometime during the early 90s. My 94 S&S fits my 05 truck (width wise) just fine with no mods. I do have to stack 3 sheets of 1/2" OSB under it for adequate roof clearance though.
That said, it depends on the camper as to how hard it is to narrow it to 60 if it is 65" wide. I did it to my old '72 so that it would fit my 05 truck and it just took a Saturday with a Sawzall, some plywood and a lot of patience.
I have re-fitted the original bump-stops on the front on our Lance today-----when putting the camper back on the truck, I was amazed at how close it came to hitting the rear lights--less than 1/4 inch clearance !!-----next time its off I will put a strip of 3/4 board against the headboard.
I also added a 2'' piece of polystyrene under the 3/4 ply board in the bed to help protect the cab roof from further damage ! ( I have removed 1 sheet of board) The foam board is lighter----we are away for this weekend. so will see how it settles down.
Nigel & Pamala----Suffolk UK
Thank you for the advice. I did have to put plywood in the bed only to lift the camper off the tailgate opening on the bottom corners, they are rounded and not squared. Our first trip was to Fort Francis Ontario from the Lindsay area of Ontario and took the route around Lake Superior... couldn't feel the camper on the truck really at all and towed a 16' fishing boat. Thanks again