Most of the roller bearings for the 47-59 trucks are NO NAME Chinese bearings. If you search hard enough you might find a set of Japanese MBS bearings. The ball bearings do not have a direct crossover bearing. The after market brake companies had the roller bearings created to fill a need.
My advise to anybody that is considering using the roller bearings is to buy an extra set and keep them in the truck. In about 50,000 miles of daily driving I have been through several sets of the Chinese bearings. When the bearings failed they also wiped out the hubs and the spindles. Take extra time to examine the spindles for [ab]normal wear. Most the ones I have been coming across have had the inner bearngs score the spindle.
If there is any evidence of the bearings that have spun on the spindle or in the hub... replace as necessary before doing the bearing/brake conversion. Any play whatsoever can cause catastrophic failure. Ask me how I know!
John
