You can either use a FM-146 or a M5OD. It most likely came with the FM-146, you can tell by looking at the bottom of the transmission. If it has a flat plate with a drain plug its the FM-146. If there's not flat plate it's the M5OD.
The M5OD is the superior transmission.
You can also use the FM-145 if absolutly necessary, but it is 2" shorter so it would require a few mods and is not a very desirable transmission.