IIRC, the MR-Gs are a different thread versus the Hurst
From what I remember Mr-Gs are 1/2-13 versus 3/8-24 for the Hurst, but that memory is from over 50 years ago ..........................
I have a couple of Hurst handles that are 3/8ths. Mojack has a Mr Gasket that is 1/2.
I will go check my Mr Gasket shifter out and see what it is threaded for but I was thinking 3/8. not sure.