Standard To Auto Transmission

I have a 1978 Ford Ranger. It needs a new Clutch and I figure I might as well change it to a Auto. It has a steering columb mounted shifer.
Other than the Transmission, what parts would I need, and how long would it take?
Also, what could I get a Auto transmission out of to work in there?

Thanks Man

1. I think you need to re-register and get a new EPA sticker or somthing to switch transmission types; 2. it seems like you are asking about getting a used A/T? I couldn't find a used 1990 A/T and had to re-buld it myself. I only get 40,000 miles on re-built transmissions. I'd love a stick in my Ranger. It would last for ever...