Outer Limits 4x4 Board

im just after some suggestions or advice on how to go about building a king cab kind of set up on a shorty i want to make use of the fibre glass canopy bolt holes aand then cut around a foot (300mm) behind the door then some how graft on a fabricated cab utiliing the most of the original cab as the floor and what not i want to fabricate a four sided box to fit over and be attached hopefully completly with bolts like the original canopy any help advice or suggestions are greatly appreciated
Cheers Bourkey