If you already have a pair of roof racks they can be used with slight modification. The hard part is getting access to the inside of the fiberglass roof. I used a late 80's set of Thule racks. Basically I just removed the part which goes around the roof gutter, and drilled 4 holes into the part which sits inside the roof gutter, and matching holes through the fiberglass roof. I used U bolts so I would have a few more attachment points. Big thick washers inside and out.
The problem is the insulation on the inside of the van. Mine had a 2 inch gap between the fiberglass and the paneling which covered the insulation.
I wound up removing all the foul smelling foo foo velour paneling and insulation to maximize space up there.
One of the reasons I decided on a full size van with a higher top so was that I could lock my 9'7" Longboard inside. I Basically always have my 9'7" and my 6'8" on the inside tied up to the roof, and found little use for my roof racks. I have stored a 10'6" up there. I noticed a 1/2 mpg drop on the highway. I removed the racks, bondoed the holes and have no intention of putting racks up again.
I like the fact that it doesn't obviously look like a surfer's vehicle anymore, and find I get waved through more checkpoints in Mexico without boards on the roof.
Right now I have 4 304 Stainless steel pad eyes on the verticle portions of the roof, and if I need to put something up there, at least I got attachment points. In the folowing pic, all those hollow cedar boards I made would fit inside, 3 and four deep along the roof. Along with all the tools and materials required to build one, with enough space left over to be comfortable camping from it. I love vans.
