How many using an A500 overdrive ?

The RE series are fully electronic. You need a stand-alone computer to make them function.
I had a 46RE for sale for awhile here...It was a rebuilt unit with an expensive converter and I was lucky to get $200 for it.
Hold out for a RH unit.
I have an RE here that I need to rebuild and put back in my Durango, I have way more than $300 out on it so far and still need the brass thrust washers all the snap rings and the rebuild kit for it plus a fresh converter before I can reassemble. Probably gonna have to wait till tax time to be able to get the funds....
That said I have an a500 sitting here collecting dust likewise waiting for $$ for parts ( it was a working pull but had lotsa miles) that I'm debating on putting into my 85 d150... Came from a 91 318 Dakota that I parted out because of rust