I think WT, the company, still exists. From them you should be able to obtain the necessary specifications for your tonearm. From what you wrote I am not at all sure I understand its provenance. But for any pivoted tonearm there will be a recommended pivot to spindle distance, stylus overhang, and effective length. To use any protractor that is flexible for all types of tonearms, including the Feickert protractor, you must have at least two out of three of these data points. So your job is to find those out. Also, if my memory serves me, at least the well tempered reference tonearm has fixed holes in its permanent headshell. And the tonearm mount is a single hole drilled through the chassis. So the pivot point is fixed in space and where the cartridge sits on the headshell, that also is fixed. More conventional headshells have slots that allow you to slide the cartridge back-and-forth to obtain proper alignment. In your case it may be that the only parameter you are able to adjust is headshell offset angle. That isn’t the greatest situation, but at least it limits the degree to which you can get this wrong. By the way, getting it wrong by a small factor is no big deal.
