I also recently changed my two motor mounts and also went and changed my tranny mounts as well as the flex discs attaching the driveshafts. I did it all at once since I had the car on the rack.
The tranny mount was also torn too. It is a real soft mount. If tranny fluid gets on it, I think it would wear out quickly.
As far as your overheating problem goes, have you tried changing the thermostat out again??? I had a bad thermostat right out of the box. It was hanging.
Hope this helps.
1987 260E Charcoal Grey 157,000 Miles
1987 260E Forest Green 120,000 Miles