W124 autom. tranny

[diesel friend]

Greetings,
concerned how much life is left in my autom. transmission of my 91 300D 2.5T.
The original unit - 722.418 is still in the car - current mileage 136K.
Can buy a used one fm an 87 300D sedan for $ 200.- - mileage unknown.
Prior to installing would have it checked out/overhauled by a tranny shop.
Intend to keep this car for a few more years and therefore wondering whether this a good way to go.
Will the tranny out of the 87 300D fit and work correctly in the W124.128?
Has anybody done this change?
Thanks for your help.
PS searched the Forum but could not finds answers