The HQ-WB power steering boxes all have the same external appearance & are all interchangeable. Over the years there were many minor internal improvements & changes.

The early boxes had bronze pitman shaft bushes, these were upgraded to encased needle roller bearings, from about 1975 onwards. We always fit needle roller to all boxes when rebuilding. The HX had the lightest torsion rod, resulting in the least road feel. The HZ/WB were revised for RTS with improvements to the spool valve. These later boxes are the best, but nearly impossible to distinguish from the earlier ones.

Since most boxes out there would have had at least one rebuild in their lifetime, the early bronze bushes are now rarely seen.

Dr Terry.