What transmission do you have, and what type of area do you drive your car (flat, hilly, high altitude, etc.)?
Ford Motor Co did a good job of matching the factory gearing to the vehicle weight and engine power. I would be cautious before making big changes.
The reer bolt pattern aso changed around that time My 51 merc rear has 5/5 pattern and the 52 has 4.5 I think might be a year off
Gramps