Heater Demister FRUSTRATION!!!

I am still not getting it. If my dash is in fact a 1973 and I have apparently the 1973 controls why will the screw holes in the dash not line up with the heater/demister controls I have.
All 3 of the controllers I have do not mount up to the screw holes in the dash. WHY?
The screw holes in the dash are 3 3/4 inches apart.