OK, I don't think we are out of the woods on this yet. I do my best thinking at 2 AM when I can't go back to sleep.
So the slider actually has to go on first. here's why. To put the slider on, you have to basically put the bottom outside edge on the outside of the pinch weld. Then you roll it up into place and the back main section goes on the inside of the body. Hope that makes sense. That's how I had to put them back on after taking them off. So you cannot install the Amp brackets first.
On the slider, it mounts with the 2 large bolts you can see that go into Rivnuts that are mounted to the body. Under those two holes, you can see a larger hole in the lower section of the slider. Inside of that hole is two smaller bolts. These go thru the holes in the pinch weld and screw into captive nuts in the sliders.
But I may have a solution I had been working on. Just need more time to figure it out.
My solution is basically this. at the two end mounts on the slider, you will need to cut out the lower section to a width that is slightly wider than the AMP brackets. You will use the same mounting holes for both the slider and the AMP step. You then weld back in a angle support bracket that you wound up cutting out. Make sure the AMP bracket fits between them. On the AMP bracket, near the bottom, which you can see in the second picture I posted above, near the top section of the bracket, is two holes. The bracket is upside down in the pictures.
On the AMP bracket, you will need to drill out those two holes to a larger size. I'll have to check, but you may also need to machine a flat spot on the back side so the bolts will have a good flat mating surface. You will need longer bolts that will go thru those two holes, thru the pinch weld holes, and screw into the slider captive nuts. You are basically sandwiching the pinch weld between the slider and the AMP bracket.
Hope that make sense. I'm waiting on the missing support brackets for my steps before I proceed any further. I still need to remove my sliders again and see if there is going to be any interference between the actual step and the bottom of the slider when they are in the stowed position. That I think is the only remaining issue I am not sure abbout.
Hope this makes some sense.