all you have to do is swap the input shafts out. you can use the input shaft from the factory th400 . i know for a fact because i have done this twice. just be very carefull and put the parts back in as they came out. the dounfall to the 208s is they will leak all the fluid tru the inside of the output yoke, and over time you will be running dry if you dont check it now and then. i have swaped input shafts from the th350s and covert them for the sm465 4-speed. its very easy to do. as for the adapter, all mine where 6 bolt
good luck...........