Anyone install three speed with overdrive behind a slant six

Its a A833 4 speed overdrive has three levers excuse my ignorance years ago we called them three speed with over drives. If anyone knows all the particulars I would appreciate there responses. I will need a shifter which one works the best stock a body four speed? Can I use the stock three speed bell housing. Just trying to come up with a parts list. Thanks in advance first slant six car that I have not converted to V8. I want to stay with the slant six just do not want to waste time looking for the wrong parts.
There's a machined pad on the passenger's side of the main case. It will have PP833XXXXX or some such. If you can post all those characters, one of the boys will decode it.