Ken, as I understand it, the front inner CV can be replaced with the same CV used on the rear half-shaft but there is a limitation: the front CV requires a greater operating angle than the rear CV's were designed for. So if you rarely go off road, where extreme axle angles are possible, you will probably get away with using rear CV's on the front inners but be prepared to replace them more frequently.
-Larry

KENWILFY@AOL.COM wrote:

Had a question about the inner front CV joints for a Syncro Vanagon.  A
customer of mine insists that these are the same are the rear CV joints
(inner and outter).  However in my parts computer we have two different part
numbers.
251 498 103A,   Joint Kit, Inner FT
251 598 101, Joint Kit Rear
I have a picture of the front inner joint kit and they look exactly the same.
 Anyone that knows for sure that these are the same please email me.

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242