833 4-speed change over

I am putting this in a 71 duster 318/3spd. Making a 340 4speed, so I have many of the components and will sell or store the rest, I know I need the a833 and linkage possibly the bell housing, I have been told the 4 speed won't bolt on the 3 spd bell. The 3 speed bell has another set of holes so until I pick up the stuff. I won't know what I need. I know I won't need the hump or pedals and the old 3 speed with linkage. Thanks KYJOE 1969 and FABO.