Well, you're lucky that the first generation overdrives will both bolt up and can be made to shift into overdrive. That would be the original A500 and A518, also known as the 42RH and 46RH. the "H" is the important part, as the later 42RE and 46RE were electrically controlled, while the "H" models are hydraulically controlled.
I'm not 100% sure of the years, but definitely the earliest throttle-body units will work.
I'm not 100% sure of the years, but definitely the earliest throttle-body units will work.