-- Last Updated: Mar-18-13 9:20 PM EST --
Any decent welding shop can make you any kind of rack you want, designed to attach to any kind of roof that you wish. The livelihood of such shops is founded mostly on their ability to design and build things, and much less so on the methods used to connect the pieces (just like being a good carpenter involves many skills that are more important than being able to make cuts and drive nails or turn screws). If you go to a place that specializes in roof racks, all they will know how to do is consult books to order pre-made parts. They can't help you come up with a solution that isn't already supported by a huge customer base. Brand-name roof-rack companies MIGHT have the kinds of roof mounts you will need, but if not, turn to someone who's not constrained by what's in the catalog.