<VV> Steering box insights ? EM and LM different designs ?

[Charles Lee]

OK, I have a 1-1/2" box wrench for the steering box worm shaft adjustment 
nut, but am I imagining that the hex locknut on that is over 2" in size ?

Maybe this locknut is special in some way, not really hex ?

The diagram looks like it may not be hex at all , so is there some other 
tool to get it off ?

I'm soaking it to clean it, so I can visually inspect, but until I can see 
it better (and light is getting to be a premium soon) any insight would be 
appreciated !

Also, in my kind of old Chiltons Corvair repair guide, it shows a completely 
different cross section of a steering box with a completely different end 
lash adjustment at this end, but it may be an EM, that may have a different 
design ?

Thanks for any insights !

Charlie