73 dart swinger project

The overdrive A833 would be perfect. Its pretty much a 3 speed with 4th being the over drive gear. There pretty common & cheap, just look for an aluminum trans. They were made from '75- the mid '80s. The later ones I don't recommend being that they have longer tail shafts and come from trucks, these can be used for B & E body purposes. Just get one out of a late A-body or an F-body. those are just bolt in (minus all the stuff required to convert to a manual trans)