[Vwdiesel] Hudson questions

[William J Toensing]

I have a question that one or more of you may be able to answer. Have just done a brake job on my 1954 Hudson Hornet (which is for sale-$16,000) & found the rear axel nuts were stripped & the rear axel threads show wear. The threads are 3/4"x 20 or 3/4 inch, 20 threads per inch, not the standard 16 threads per inch. I have located & ordered some 3/4"x20 castellated nuts. However, if they don't hold, I will need to retap the axel threads with something slightly smaller to avoid having to replace the axel shafts. Any suggestions as to what threads & nuts I should use? I was thinking there might be a metric thread that might be just slightly smaller than 3/4"x20 with about 20 threads per inch but larger than the next smallest SAE size. Hopefully, the 3/4"x20 castellated nuts will hold but if they don't, I want to be prepared. My research found that the 3/4"x20 is not a standard size & no local parts house has them. 
Once I get the Hudson up & running, I can get to work on my Dasher & Quantum diesels.