another idea............
Not sure if this would fit your brothers need for space, but it works for me pretty good. I have the 163" wheelbase regular cab. However, I had a custom bed made with a storage box on the side for my wheelchair. The bed was built up high enough in the front to put a fiberglass sleeper (the kind that usually mounts at the front of a regular pick-up bed). This adds several cubic feet of extra storage space. I use it as a "catch all", jackets, CD's, blankets, briefcase, etc.