If you have ever installed front wheel bearings on an older vehicle that used tapered roller bearings, it is basicly the same concept, except you are using shims. Zero to a couple thousandths of play is desired. If they are too tight, make sure the bearing races are seated fully before changing shims.(no burrs/dirt) The original shim will almost always be correct unless someone changed it.
I used the original shims on my old 1830. didnt check them during, just cleaned the hubs, installed new bearings, races and seals, packed them with grease and reassembled. Bearing play was correct on all hubs without changing spacers.
be sure to pack them with grease before assembly. DO NOT try to use the grease zerk on the hub to grease them initially, as you will push the new seal out.