Interesting Max, I read about that somewhere before and had forgotten about it
I think HD was the one that changed the numbers - because it was one of the head honchos initials (edit, just looked and apparently David Hegland was MD at the time)
The FX designation has been of some speculation - often it has been suggested car dealer who was sick of writing 48-215 and abbreviated it.
However, another more believable reason was detailed in one of Don Loffler's Holden books.  
Apparently (according to one of the engineers working for Holden's at the time) stated the FX was name from 1951 ish onwards when they changed the suspension - F for fifty  X meaning cross member.
We will probably never know definitively as most of the people who were involved have passed away 
Last edited by Tyler; 11/03/20 01:38 AM.