Check out United Specialities. The brand name they use is Trendsetter. I believe that they offer a conversion package on the customers chassis.
What made me remember this was the NHRA weekly National Dragster showed up yesterday. This was the first issue for the 2004 racing season. There are 12 pages of advertising in the classified for race trailers, toterhomes and motorhomes.
which is the site for Cap's Coach and Trailer is shown. In their adv they have the United Specialities logo. A small footnote says "Built on DOT Certified Used Chassis".