The National HDT Rally for 2008 will have seminars on the issues of building your own bed, singling out a truck and a variety of other things. Registration won't open for a while yet, but the date and location have been set as Oct. 4-11, 2008 in Hutchinson, KS.
Last year, there were over 60 rigs from around the country.
There are several blog websites from guys who have done just what you're looking for.
Mark & Diane
Fulltimers Class of 2008