Buy the Cen Matrix rear axles and you won't need shims for the rear. I may have a set somewhere around my garage that I can sell you. PM me if your interested.
For the front, go to your local hardware store and buy a small package of 8mm washers. You will need 1 washer for each universal. You may need to add a .1 shim to remove any backlash/play from the hexes. Using the washers is a lot better that using a bunch of shims IMO.