The bedtop type tiedown is a thing of the past. There isn't enough wall strength to support them in newer (post 1985 or so) pickup beds.
IMO the
Torklift http://www.torklift.com/ camper tiedown system is the best because it goes directly to the vehicle frame without stressing the bed at all.
Illflem is right about problems with width. Older trucks had tailgate openings of 64" or more and campers were built to fit. Newer trucks (Dodge anyway) have a tailgate opening width of 60". Older campers are often too wide to slide in. Some people have had success in cutting into the camper and rebuilding the lower sides where they fit inside the bed. Some use fiberglass, some wood, whatever works. It depends a lot on the locations of holding tanks and buildins in the old camper. A shower, for example, would be tough to cut and reduce.
You'll probably find that the old Dolphin camper is way overweight for your truck, at least insofar as a strict reading of the GVWR and load capacities is concerned. A 4x4 QC 2500 can only carry about 1200 lbs in the bed they say. The truck will handle the weight of that camper without a sagging, but it won't be kosher if anyone should ever raise the question. This is all stuff that you'll have to make your own choices about risk as it could go to liability issues should there be an accident.
First thing - measure your tailgate, then measure your camper. Good Luck!
(I have a 8. 5' alpenlite rated at 2300 lbs. on my '97 2500. I did put in air-lift bags but don't think it needed them really. My camper makes my truck overgross by the factory rating though I did have the registered GVW changed up to 10,000 lbs. Washington state allows this, and I figure that it'll at least create a troublesome counterargument to someone making a case against me. Maybe I'm just full of hope and hot air too. )