Any tips or hints to replacing the rear differential mount?

It's pretty straightforward. You'll get the rear of the car in the air safely on jack stands, front wheels chocked. Then you'll use your floor jack to lift up the differential just enough to take the weight off the rear diff mount. Then you'll use a 22mm socket to remove the two large bolts holding the mount to the diff cover, and a 13mm socket to remove the four bolts that hold the mount to the body of the car.

Then simply reverse to install the new mount.

Here is a guide that covers rear axle replacement. As part of doing an axle swap you have to remove the diff mount, so it shows how that is done. Scroll down past the part where it talks about removing and hanging up the calipers (you don't need to worry about any of this) and you'll find four of five pictures and notes about diff mount replacement.

http://www.peachparts.com/Wikka/W123RearAxles

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thanks for helpful prompt replies!