For reference, I've got an '03 2500 144".
There is a 'shop-built' cargo wall installed right at the rear edge of the slider door.
From the wall back to the rear doors, is just about 7' 2"
My wall now has a 6"x40" high hole in it, so I can fit a '99 R1100GS straight in. I could fit it in by angling it, but it made for interesting loading. There is about 3" of beak & wheel sticking thru the wall.