Does anyone know a good six speed automatic transmission that can be used with a 1996 magnum 5.2.?

I have an original 5.2 and auto transmission from my 1996 dodge ram 2wd. I am going to be installing it in a 72 duster and wanted to see if there are any possible six speed AOD options to replace the original weak transmission. I have all the original wiring and controls for the motor and tranny just looking for something stronger and more drivable than the original tranny.