Been there, done that. No, no, no. Actually, STILL doing that.
My ongoing project began with a rolled Explorer 91 Sport 4x4, and a 1990 2 wheel drive regular cab Ranger. The cab mounted almost perfectly, except for the body mounts behind the seat. I got some buddies to help me weld a 2x6 (1/4 inch thick) boxed beam to account for the difference. The frame is lower on the explorer to give room for the back seat.
It's still a work in progress. Had to knock 6 inches off the bed up by the cab (plasma cutter works like a knife cutting through butter), since the Ex is that much shorter than the Ranger. None of the mounts out back line up with the bed mount holes. So for the time being, I spot welded a 3 inch I beam on the frame to line up with a set of holes it he back of the bed with a couple of mounting tabs for the bed to bolt up to. I used a couple of pieces of pipe up front with nuts welded into them to hold up the front of the bed. These braces are just temporary, considering the bed isn't quite aligned front to back. I need to drop the back end about another inch or so. I did this because I got tired of looking at half a truck on the frame and half the truck off the frame. I haven't come up with a good solution on permanently mounting the bed, since I still want to re use the rubber mounts to minimize vibration and still be able to use the bed to carry stuff.
Here's the ugly on swapping shells. They are heavy, so you need a a lot of buddies to help you pick the shell off of one to place on another. The trick is to clear the engine when pulling each of the shells off. I used two A frames and a couple of come-a-longs. They made life much easier. Disconnect all the harnesses off the body, disconnect the brake lines from the master cylinder, e-brake, shifter linkages, steering column, the radiator, grounding straps, battery, and air box. Removing the plastic wheel wells let me get a better view when pulling stuff apart. Then, just roll out the old chassis and slide in the other one. After that, it's all a matter of re-running all the wiring harnesses back up to their mounting locations, and connect everything else. If you can do a body lift, you can do the swap, except for the welding and cutting part (That's what my buddies are for, because I didn't know how). All of the harnesses hooked right back up in my case. I used a 1354 manual case to avoid having to decipher and run wires to the t-case.
Going on 3 years with this project, and still not done.
This just what I have gone through so far, an extended cab on a 4 door ex might have you lengthen the bed??? Or probably loose the majority if on a 2 door.
Here's the disclaimer: I probably forgot to mention some stuff, so you just have to pay attention to the details. You have to be totally sure you separate what stays on the body, and what stays on the frame. I used the most basic of tools, since like most of you I'm a weekend warrior.
Hope it helps.