Walk through cab/bed??

[manimal]

Anyone remember these from the 90's??? How hard would it be to reverse that?
For those who dont know what they are, it's when you cut the back of the cab and front of the bed wide open, add a shell so you have a "walk through". I am looking at buying one, but the rear of the cab is what I think would be the hardest part of "fixing" it. the front of the bed would be very easy, just replace the headboard.
Thanks