I assume you are talking about a flat floor DJ with the door cutouts.. You probably could splice in the "door area" from a good donor, but you will still have no toolbox....If that matters to you. It will make mounting a passenger seat a little interesting, but not impossible.
Hey show us pics of both tubs , top and bottom , and we might suggest a different path, like transfering the rear half of the DJ tub to the front of your 3A..
In either case you should be well practiced on your measuring and cutting skills and be able to do some good sheet metal welding.