Got 'er done today. Well, almost.
I went to the auto parts yard last weekend and found a roof rack that was damaged and took the gutter mounts off of it. They may not be the strongest, actually on two of them, the welds are cracked, but they'll do for now.
I thought I could just mount the rack to these mounts, but when I put them on my truck I had 48" between the mounts and the roof basket was only 40" wide. So now I needed a couple of bars to bridge the gap. I thought about getting the damaged crossmembers from the rack these came off of, but they were angled and too long and would have to be cut and joined together and just too much work. I was going to got to Metal Supermarket and just see how much 3" aluminum channel would be. Fearing that it would be expensive I went to Home Depot thinking I might find something there and did find some clearance aluminum railing pickets that would have been strong enough, but again they were not long enough so I would have to join them together.
I had concluded that the aluminum pickets from Home Depot would be the best option as they were under $2 each but since my work is near Bucks and I get Friday afternoons off, I decided to stop in to see what they had since they do not post their inventory online. Well, I was in luck again. I found a an with another roof rack on it.
This one is really nice and strong and just what I needed, Unfortunately, it was not a gutter mount. It was bolted directly to the roof of a van, which is kind of too bad because the mounts are 1/2" thick aluminum.
As you can see, on the bottom it is grooved to accept bolts so you can slide a bolt in and move the attachment points around without drilling any holes in the rail.
So I took my gutter mounts and drilled two holes in the top of each of them and attached my rails.