Hi Paul, John Emmanuel who developed the modified steering head had fitted taper roller head races but told me that he did not think it was necessary. I can get this done for you by a local engineer who borrowed three different steering heads from me in order to make the jigs to make this relatively easy. The steering head has to be removed from the oil tank which is actully easier than most people think. My own feelings on this are that if you have cup and cone bearings which are still in good condition then there is no need to do this. However, if the cup and cones are worn or their housings are loose or damaged then the best way to go is to convert to taper rollers. Apart from handling they have the big advantage of not having ball bearings being loose and falling out all over the floor the steering head has to be dismantled. The alternative,if you want to do it without getting the steering head machined there is the VOCSC taper roller conversion, which is based upon a German design and that requires no machining of the steering head.
Hope this helps
Hope this helps