Interesting idea on heating/freezing to get the bushings in--you must have an understanding wife!

As far as tightening the rear nut, this is indeed a perennial problem. I'm a believer in having the car sitting on its tires before tightening. I did the following to make it easier.

0 Put the tires on some kind of ramp to make it easier to work under the car.

I have a set of 2x12 plank sections that I use as "insurance" when I have the car on jack stands. Each is about 14" long. To do the bushings, I just stack 3 or 4 of these and lower the car tires on them. Gives you room to work.

0 I just tighten the left side nut with a wrench, guesstimating on torque.

0 For the right side, I removed the three-bolt pocket and cut a 1/2" by 1 1/2" horizontal slot in the pocket. This allows me to reach a wrench up inside the pocket when the three bolts are tightened, with the car on its wheels, and tighten the nut. Works great, and hasn't seemed to weaken the pocket.

Just make sure to put the slot in the right place (can't give you exact directions, just eyeball it) and make sure the slot is long enough so you can work the wrench back and forth.

One other thing--this slot could interfere with the add-on lower brackets (not sure, but this is a possibility) so it might not work with such cars.
HTH,

Dschwied