Who has a Hurst Billet-plus shifter?

I just purchased a Hurst billet plus shifter for my 85 GT.It has the short black handle...installed it ..works great..went to Summit Racing and bought a Hurst white shifter ball for it...now...the ball will thread down on the handle, but the locking nut that came with it will not even start to thread on this handle..I even tried the nut on my stock shifter..won't thread on it either.. what gives..I can't use the ball without the locking nut. Anyone know a correct size nut for this shifter?
 
I just replace my Hurst shortie w/ an MGW. The threads on my old one are 12mm x 1.25 pitch. It's an older shifter so I don't know if they have changed the threads over the years.

I contacted Hurst and they said ONLY Hurst handles will fit their shifters. :shrug: