if i recall correctly, the reason for the spacer is to push the hub out, which creates enough clearance between the rotor and the dustsheild. the spacers i made were 3/16" thick, 2.5" O.D., with a 1.785" I.D. you won't be able to use the outer external snap ring on the axle, so you will have to use a bolt/washer, and a little loc-tite. this set-up has worked flawlessly for 7 years, and it saved me a few buck on the conversion...if anyone wants to try this route, i'd be willing to turn a few more spacers...