Just an update/completion.
Bought the Husky brand rails and brackets for downsized truck, which is made for the Dakota and Ranger. Finally got around to installing it today.
Installation was easy enough. Set the hitch on top of the rails, measure ( and measure and measure!) and drilled the 4 holes through the bed for the bolts to the brackets. Add the spacers where needed, and then drop the bolts down the bed rails.
The next part is to loosely bolt the brackets up to mark the holes that need to be drilled to attach the brackets to the frame. These holes are supposed to be a 17/32" drill bit, but only had a 1/2" available. Just drilled a pilot hole, and then the 1/2" bit, and then removed the bracket so I could wobble the hole a little bigger. Not ideal, but the wheels bolts all seated properly.
On the driver side I had to watch for some electrical lines and the brake line, passenger side was clear.
The center of the hitch is back an inch and a half of the center of the axle, which isn't exactly what I wanted, but it still tows like a beauty. Weighed the camper (no water) and crossed the scales at 8920 pounds, giving me about 600 pounds of GCVW before I'm maxing out according to the book. Has plenty of power still, holds 'drive' well on hills and overpasses at 60 and 70 mph. Truck and camper sit very level, looks well together. Rear springs are tired at 140k hard miles, but still rides great.
Overall, gotta say I'm glad the camper I found was a 5th wheel! Now I just have to buy a goose neck plate and covert my car hauler over....