Do a quick site search on "ReTrax". They are excellent units, custom made to handle short beds, and work well with the utilitrak system. For best results, it requires you to drill 4 holes, 5/16" dia, IIRC so you can bolt it in place. The rails remain free for use.

Other companies offer great units. I sold mine so I could put a canopy on my Titan's bed. My unit is by ARE, excellent quality, form and fit.

Good luck.

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2005 Titan KC SE, Helwig, True-Track, ARE MX Canopy