a long time ago I bought a few rear axle parts. I think there is a whole differential and a couple crown and pinions. I think thy are older, maybe for a PV544 or 444 are the 444 or 544 differentials smaller than the ones used int he 122?
If anyone is interested I will try to get them out for pics. Im in Vancouver and they are quite heavy but I just realized Ill probably never use them and they are probably hard to find parts. If I recall correctly there is a diff and two sets of gears with new crown and pinion for an older volvo , then there were some newer gear sets like my 122
I used a set that gave my amazon gearing like a 123. I think there is also a stock set for an amazon that are new but one tooth has a slight chip on the crown. it might be inconsequential in actual use. Ill drag the parts out and verify if someone wants to get into a rebuild of an older rear axle. I don't have the spider gears for the 122 but I do have a set that is older and I think from an early volvo.
I seem to recall that someone said there is an earlier diff that splits sideways.. the amazons have the typical tin cover on the back.

when I pt the gears in my 122 i just used the best diff I could find but did all the bearings and set up the new crown and pinion and it made a big difference to the backlash.. I know most just find another axle as they seldom fail but they do wear. getting rid of the backlash made it nicer for drivability especially at slow speeds.