I had my Syncro tranny and my Barndoor reduction boxes done by Gary Zink of Gary's Transaxles in Kent WA.  Most local mechanics send their trannies to him.  He does it all.  He uses the newer style 3/4 gear with relief cut so they don't break up like my original did.  I watched him do the reduction boxes on the Barndoor, and he really knows trannies.  I don't know his email but his phone number is 253-631-4004 or  253-631-3600.  Happy veedubbleyewing.   
Bob Freeman
North Bend, WA