Bendtsen's
http://www.transmissionadapters.com/ford_y_block.htm has a AOD to Y-Block adapter. Cost you ~$850 for the adapter kit plus the price of an AOD. I think you also have to have the driveshaft shortened. Not sure on that.
Flat-O-Matic makes the C-4 to Y-Block adapter.
http://flat-o.com/carproducts/yblock.htm That's what I have in my Ranch.