My dads friend thought he had a set of 3.91 gears for my 72 charger, but he figured they would not go with my 12 bolt. So then he found a set of 3.55 gears in a 14 bolt out of a 73 road runner or satellight?

I am just seeking some clarity to figure out what a good set of gearing ratio would be suitable for my 72 charger. Curious who has used what and what they think of it?

thanks Josh K.