These RHD issues can be confusing. I bought a RHD sector from MAC's and it was correct and was good quality. I also bought a drag link rebuild kit which included springs, cups and end screws. The end screws appear to be 1 1/16-18 for the RHD drag link and 1 1/16- 20 for the LHD or US domestic drag link. Why they would be different makes no sense but I thought this information might be useful to others.
I rebuilt the steering box on our 1941 C11ADF (RHD) military station wagon with a worm supplied by Mac's. It seems to be of good quality and adjusted correctly.
best to use a 37-40 steering box, You only have to ever so lightly slot one of the 3 mounting holes and you are in, be sure to use only the 37-40 drop arm . if the column length is an issue , have it professionally shortened,
You need to contact James at sales@gothamautoparts.com he is the man that knows Right Hand Drive Fords back to front and has in stock all the RHD parts. I have been buying RHD stuff off him for many years. Dave
Thanks everyone for your input and advice, I have managed to secure a 36 RHD worm and sector with its bearings from Brian in New Zealand, hopefully it will arrive and sort out my steering problems. Thanks again guys
Viv.