Other than Andersen and a 6.3' bed you should also consider the shape of your 5ers nose (it should be sculpted in the so-called 'max-turn' style) and the length of your pinbox is relevant. Some are short some are so-called 'extended length' etc. Lastly is the height of your truck bed sides. For this last one, if the pinbox clears the top of the bed rails you may not need to reverse the Andersen adapter and that'll give you a full 8" more cab clearance.
2016 Wildcat 295RSX - 2015 GMC 2500HD DblCab Duramax/Allison 4x4 Z71 6.6' Bed
Maxxis 16" E; Ride Rite AirBags w/AirLift 1 wireless compr; Adv.Folding 4 Cover
Andersen Ultimate II Aluminum 5erhitch on Reese Flipball w/Curt 4" offset ball
LCI Ground Control 3.0 4pt + 2pt Elec.Rear stabilizers; 3 Slidecovers; 10ft. Portabote
6000# Dexters; mor/Ryde CRE3000 w/HD Wetbolts; King Dish Tailgater; 5hp Outboard
Dual A/C; Furrion 48 Rear Camera; Champion 3100 Inverter w/Extended Run