hello RFP
you must be one of the guys looking at that used camper in Portland ?
Your year truck is a weird one -- you will have to follow the same guidelines of anyone with a Tundra looking for a used camper.
Your tail gate does not have the standard 60", so you will need for find a used camper that was built in 2001 1/2 or newer (ex: 2002, 2003, 2004, etc.)
Here is the general rule of thumb for your truck too ...
Toyota T-100 & Tundra Trucks will only fit the newer style ”full-size” Four Wheel Campers. We narrowed the base on the Hawk & Grandby in the middle of 2001 especially for the T-100 and Tundra owners. If you have a T-100 or Tundra and are looking at used campers, take some careful measurements of the camper and your truck bed before you buy. The Older Hawk & Grandby Models unfortunately will not fit. The tailgate opening on the Toyota is usually the biggest factor. The older campers are 60" or 64" wide where the camper will be sitting in the tail gate opening. The newer campers are 58" wide in the tail gate opening area (specifically to fit the T-100 & Tundra Trucks).
next time you find one, just have the owner measure the rear wall of the camper in the area that sits in the tail gate opening.
If it measures 59 3/4", you are out of luck.
If it measures 57 3/4", you are good to go !
hope this helps
.