There is a place in Minneapolis called Surplus Bearing Store (surplusbearingstore.com) that seems to have just about every antique bearing one can specify, at very low prices. I found NOS Timkens for 51-55K front wheels of the original numbers. Apparently these have been accumulated from a wide range in years, as the boxes vary quite a bit. All the bearings I got were in new condition, however. Very fast service and free shipping. So if you're having problems finding something, give them a try.