Bill:

I recently went through a similar problem in trying to adapt my 84 
Woflsburg Vanagon with a Country Homes Camper to carry a canoe - it is 
already equipped to carry 5 mountain bikes, one mountain bike tandem, two 
tents, a Burley (kids buggy), and a duffle full of helmets.  As you can 
imagine - adding a canoe was a chore.  I looked all over the world for a 
set of the old Thule uprights - the kind that have holes for adjusting to 
a variety of heights or for installing multible racks that could be used 
for mounting a series of boards.

After calling Thule in the U.S., Canada, even Sweden, and emailing 
several lists and individuals - I gave up trying to locate a set of 
uprights and fabricated my own.  They look something like the following:  
              ==
            //  \\
           ||    ||
           ||    ||
           ||    ||
           ||    ||
           ||    ||
          //      \\
         //        \\
        //          \\
       //            \\
      ||              ||
      ||              ||
      ||              ||
      ==================
      ==================

This is not the best representation, but most email programs will not 
accept graphics.  I was able to obtain a sketch from Thule of the 
originals, but since no parts were available, everyting had to be 
constructed from scratch.  Works great.

Fred