That's kinda tricky, as there are different gear ratios, and the later trannys have different electronics. There are also some minor differences in the side cover, as far as trans mount usage and such, between the different models. The side covers will swap out easily, tho. You would need to verify what ratio your car has, and then verify what the other trans has, in order to be safe, as the incorrect ratio will NOT work...it will set gear ratio error codes, and put the trans controller(PCM) into "failsafe" mode.
The RPO codes will tell you what ratio the car has originally. Look for the service parts label...sometimes they are on the board on top of the spare tire in the trunk, or it may be on the trunk lid(underside) itself. Not sure where it would be on the Eldo.
I'll look and see if I can get the codes that were available for your year Eldo, and post, so if you can find the service parts label, you'll be able to determine which one you have. It may be a while before I can get that, since we're sending my shop 'puter to the Dr. tomorrow... :<( It's sick....

Also, the dealer can tell you what ratio the car had...they just need the VIN#, and a parts/service guy that is willing to check it for you..