Depending on what size camper you're looking to put in the bed while towing, you may want to consider the 1 ton (dually). This is mostly because the weight ratings of load-range E tires, is being pushed to the limit with a big camper and decent amount of trailer tongue weight.
For further reading on this subject may I suggest:
http://www.pirate4x4.com/forum/showthread.php?t=504463
The 12 valve Cummins with a manual trans is the ultimate in reliable, durable, efficient, affordable diesel pickups IMHO when built smart with a few power modifications. And as a bonus on the early 90's models you're looking at have less of the plasticky, creature comfort interior parts and features found in the mid/late 90's Dodge trucks that often fall apart around this super studry powertrain combo.