4 speed/ 3 spd OD

The 833OD started in 1975 so Brewers is correct. As a general 1975 833OD's were cast iron and starting with 1976 they were aluminum.

Also you hear a lot of people call them 3speed overdrives (my dad's one of them). It is a true 4 speed because all of the speeds are gears. If the trans had a planetary overdrive unit on the back then yes it would be a 3 speed overdrive but it doesn't, all forward speeds are gears and it just happens that the 4th gear is over driven. Know one calls all of the late model manuals that have OD 5th or 6th gears overdrives so why should the 833OD be any different. The 4th gear on an 833OD is actually 3rd gear on the non OD 833.

If you have trouble trying to figure out what trans you have '64 cuda's way just take off the side cover starting from the input side of the trans if the second gear back (the gear after the input shaft gear) is smaller diameter than any of the other gears on the main shaft it is an OD trans.

Chuck