[The Radium King]

if you want to keep your rear 5-speed wheel carriers (brakes, suspension, etc.) I am pretty certain that you can fit the 6-speed hub in the 5-speed wheel bearing/carrier. otherwise i am pretty sure the 6-speed axles won't fit in the 5-speed hub. note that you also have to change the slave cyl and shift cables/linkages.

edit - reread novas post. I know it works the other way (5 speed hub in 6-speed wheel bearing/carrier) but didn't think about clearance required for the larger cv joint. dunno there. unless you can figure out a way to get the outer cv joint off the axle (don't think possible).