Daughter needs Gas mileage from 273 commando

What is this A-833 O.D. trans. I have seen mentioned ? Will it fit a '65 Barracuda? Any clearance issues ? Is the cam I have too big for this type of Trans. ? What did they originally come in? How hard are they to find ? Thanks DaveBonds , I have read Tech articles about "Cranking Pressures" I will have to give it a try on this one.....