Last I knew you had a TH350C.
Oh well.
From my notes- I don't know who to credit it to: "55-56 had 3.70 with a standard trans, 4.11 with the OD trans, and 3.55 with the auto trans. In 57 they went to 14 inch tires and then they used a 3.55 with a standard trans and 3.36 with the auto trans."