Need new differential - and exchange info

[90mbenz]

1990 300 SEL
While under the car and checking the driveline, I was bummed to find my relatively new front flex coupler is already failing after only about 30k miles. Driveshaft seems fine, but I pulled the flex coupling and will replace. I checked the differential and if an ear of the input coupler (on the diff) is at the 9:00 position, you can rotate the coupler (yoke) to almost the 10:00 position before the wheels can start to move. That whole space (9 o'clock to 10 o'clock) is free play area. This sure seems way too much to me. Car has about 215k on the clock.

Assuming I replace the diff, what choices do I have? There are a couple on eBay, but not specifically for this car. There is one for an 89 300DT and an 89 300 TE. Seems to me the TE should be the same one?

What cars share the same diff?