Installing Thule towers on a tin top Prev?

My LE lacks the sunroof(s) option, and there are no roof rails. I've done a little clicking around and there don't see to be any results on websites for rack retailers nor on Thule's site that indication how to fit crossbars to my van. There's some discussion over on Toyota Nation about installing "Top Tracks" but then clicking through to an installer's webpage is a dead end: no fitment with Top Tracks.

Any recommendations? I'd strongly prefer to use the Thule system with aero bars, a roof box, and awning. (I know it's a Ford/Chevy thing - I just prefer Thule.)