For a diff which has the clips inside the side gears (sharp edged grooves) you need axles with chamfered grooves. These will force the c-clips to expand and slide onto the axle splines when you smack the axle out and the c-clips stay in the gears.
If you use axles with sharp edged grooves with a diff with sharp edged (grooves) gears you may not be able to get the axle out w/o breaking c-clip.
If you use the diff you mentioned take the clips off the axles and chamfer the groove edges. Before you do this confirm (measure) that the grooves are in the exact same axial position both on the axles and the diff side gears to that they will engage. There are at least two different set ups around.
The stock SVX visco diff has the clip on the axle on LH side and the clip stays in the diff on the RH side
. See my axle related photo in the thread below
http://www.subaru-svx.net/forum/show...highlight=axle
Tapani