wait ur missing the entire armrest? what happened? but anyway i doubt you can directly replace the whole thing, i think its housing is welded to the subframe somehow. but the armrest itself should just pop out. anyway my armrest has broken out of its housing due to ford's wonderful reliance on plastic craftsmanship and strength. i wonder what would be a good replacement?? all i know is if i find the guy responsible for the thing's design, im gonna kick him in the nuts.
You can add the console with armrest if I remember correctly. All you need is the console and the armrest support (a big black hunk of plastic that lives under the console and forms the tower for the armrest).
Yeah its possible, theres a tutorial somewhere on here on how to do it. I just did it for my 2002 ZX3. There's three main pieces, the console, the armrest assembly and the armrest core/strut/brace thing. The brace bolts to the floor of your car and the armrest bolts to that, in theory you could just use those tow pieces and not have any center console but that would look rather silly.
Easiest and best mod EVAR! When I got my FoFo, I had the arm rest. Got in the way everytime I went to shift. Had a buddy who wanted it and we swapped. You're going the other way around and there is no difference in installment or uninstallment .
HOW TO for when you're ready [thumb]
1) Pull both cup holders out and you'll find 2 phillip head screws...remove them
2) On the rear cup holders there is a middle piece that you just pull out to find 3-10mm nuts...remove them. Pulling the rear cup holders can be tricky. What you want to do is try and pull mostly towards the front of the car portion of the cup holders.
3) When all screws and nuts are removed, take off the shift boot (IF APPLICABLE) by pushing the rear portion of the boot forward (Towards the front of the car) and up. Then take the E-Brake and pull as far back as possible. Take the top portion of the E-Brake boot and pull it up, so when you take the console out, it'll slide off with it.
4) Remove center console. Be carefull when taking out your center console and take your time making sure you're not going to scratch anything. You may have to put shifter in 4th (or into D1 if automatic) so it comes out easier.
5) When removed, look at where the 3 bolts stick out towards the rear. That is where you'll place the big black plastic support. Place on screws, screw on 10mm nuts and tighten.
6) Install new console. Screw in the 2 phil head screws in the cup holder locations. Install cup holders.
7) Take arm rest and place it on black support. You'll see in the back there are 2 holes for phillips head screws. Screw em in. IIRC there will be a screw hole for the rear cup holder. I don't remember if it's for a 10mm or a phil head, but you'll see when you get to this point.
8) Place rear arm rest cover going top to bottom and you are go to good...........Enjoy your armrestness 
If I forgot anything, LMK cause I'm going off of memory here...LOLz
MODS: If you care to sticky this in the how-to forum, I'll take some pics of the process and post em [race]