What Don said on the boxed frame. I haven't done any yet. But when I do, I was figuring on welding a [big] angle iron bracket to the frame (vertically aligned), then bolting the sliders to it. I figure that would allow better flexibilty down the road if they needed to be repositioned.

I will not look to remove mine. I want to make some and diamond plate the tops to be steps.

Big Truck: 00, 3.5, Endeavor, 5-Spd drive line in hand!
Little Truck: 87, 2.6T I/C, MT, LSDs, Tonneau Top
Her Truck: 03, 3.8, 20th Anniv, 65k
Daughter's: 06 Eclipse, Keeping it Mitsu!
FSMs: MitsubishiLinks.com