I think I would try and get them working in slots 1-2-4 like you had, tighten up the screws if any are still loose. When you mount them in your case you should be able to move them from side to side a little before tightening the screw in the pci bracket, that might let you space them just far enough apart that the fans don't touch.
If the fans still touch it won't break your gpu's using a small piece of cardbaord or something similar as a spacer, you don't want to use anything too thick as it will put tension on the pcie slots. I've seen people use fishing line to pull them apart a little too.
If you have to resort to slot 1-3-6 configuration here is a photo of long 3 way sli bridge, asrock has this long 3 way sli bridge, you can check with them to see if it is the one you'd need. One advantage of this configuration is they would run cooler.
http://www.overclock.net/t/1226191/lightbox/post/18259101/id/1067275Or you would need to get three long flexible sli bridges and connect them like this.
http://www.overclock.net/t/1226191/lightbox/post/16658110/id/773170