http://www.etrailer.com/fmr-2006_Ford_Explorer.htm
E-trailer is showing:
Curt model 31540 for "2006 Model Year only" (difficulty 5 out of 10)
This model attaches with 6 vertical bolts (4 existing holes/slots, and 2 which you drill).
Curt model 31545 for "2006.5 Mid-Year Model only" (difficulty 4 out of 10)
This model attaches with 2 vertical bolts and 4 horizontal bolts (all existing holes/slots).
Because there is vertical and horizontal elements, this increases the difficulty/time slightly.
The fact that they offer a model for '06 and '06½ seems to imply you WON'T have to cut up anything as long as you order the right model. Look at the link, and click on the appropriate hitch, and you will find a .pdf link for the "Installation details" on the right about halfway down the page.
From what I can see in the instructions, the frames are drilled differently, and that's how you can tell if you have a mid-year model or not. The '06 will have 2 existing slots on the bottom of each frame rail. These are the 4 existing mounting points, and you will simply drill 2 more behind them after the hitch is in place. There is also a large hold on the outside of the frame for fishing the carriage bolts, but it looks like there are no corresponding hole on the inside.
If you only see 1 existing slot on the bottom of each frame rail, and the side hole goes thru the inside and outside fo the frames, I think you have the '06½.
Study those install instructions for a while, and you will see what I mean.
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