This is the part number you need for the AWD 4R70W to Dana 20. Advance Adapters 50-2704A. I have this new in the box for sale in the classified section. PM me if you're interested.
To add a little more clarity, 50-2704A is another option, but it's not the ZF adapter option that hyghlndr was originally asking for:
50-4303 - aka 'ZF adapter' - works on on the 4WD 4R70W and uses the same tailhousing that came on it. This requires a custom trans mount. BC sells one that works if you add a 1-1.5" spacer on the trans mounting block. Or you can buy a F150 4R70W tailhousing that adds the 1" mounting flange on the bottom. This option is a little cheaper for the adapter kit since it doesn't come with a new tailhousing, just the spud shaft and clocking ring.
This was from a post from Doug (904Bronco last year on the others)
So if you have a good running 4x4 4R70W transmission and you do not have to go into it internally then you use the AA adapter kit (#50-2704A) with the ring. It will add an additional 1.4" to the length of your Tranny/T-case in addition to the 1.5" that the 4R70W swap has over the C4/D20. So 3" longer overall.
For the 50-2704A, you can modify your existing C4 trans mount to work with the AA tailhousing
If you are going into the 4x4 tranny or have a 2wd tranny the AA kit (#50-2704E) is used where they install a different output shaft into the trans and eliminate the need for the adapter ring. This makes the install just 1.5" longer than the C4/D20 combination.
