..This picture frame adapter sets 2" high, my regular rails measure a little over 1 3/8" high.
Just about any Reese hitch will fit, as mentioned, you may have to "tweak" on your 5er hitch some should you go the route of the GN/5er hitch prep package.
I had a hitch installer do the "tweaking" on mine due to me not wanting to screw something up, and they KNEW what they were doing....Now, due to the fact that the adapter is taller, I've dropped my hitch two holes, (just a ballpark), won't know till I hook up and "eyeball" the set up to see if I need to re-adjust.
There are two sets of slots....but the adapter will take any hitch that has the 22" front to back measurement...most rail mounted Reese match this criteria....you have two widths you can play with mine mounted to the two inside slots....there are two more slots on front rail and rear rail that will take a "wider stance" hitch, if needed.
I will say that this adapter REALLY nails down tight to the puck holes in the bed of the truck...it is rock solid...the adapter is fairly heavy....I'd say 75# or so...Oh, the hitch comes with 4 bolts and nuts to mount your hitch to the adapter, but I used my pins, which worked better....
hope this helped.
http://www1.snapfish.com/snapfish/thumbnailshare/AlbumID=6296054017/a=148038676_148038676/otsc=SHR/otsi=SALBlink/COBRAND_NAME=snapfish/
Rick, this is the album the pictures of my truck were in..I added several shots of the adapter, I right clicked on it and opened under URL and got the album, bottom row is hitch, if y'all can see it.