[OsoMoore]

Interesting, I didn't realize there were different methods of hardening. Would that cause the curved lines that follow the race's channels?

On the issue of different sized bearings - I got out my English micrometer.
All the balls were 0.75" diameter.
The outer joint's cage holes' diameters was 0.75", while the inner joint's were 0.748". That is what caused the balls to not fit through the hole easily.
On the outer joint, the diameter inner race was 2.159, while the inner joint's was 2.202
The diameter of the outer joint cage was 2.651, while the inner joint's was 2.6405.
This is surprising, because I thought both joints were supposed to be identical. I'm not sure if this is significant at all.

My question for all you CV bearing experts out there is this - should I replace both? Or is a little light scarring on the one joint OK, or I can just re-grease that one buy one and replace the other?