Thanks for the estimate on the rear refrigerant volume. Luckily I haven't had to add any refreigerant after adding in June. It is still running cold after 5-6 weeks and the short cycling hasn't returned.

Yes, I picked up the vacuum controlled coolant valve at a local parts store. The first store I visited was out of stock and second one carried it.

I didn't see a replacement 3 speed moter for my aftermarket rear blower at the link provided. I did see a replacement for the OEM front motor. The site I indicated in my original post has a 3 speed blower assembly (motor, fan, housing) with identical dimesions, but I don't know if it will plug into the existing wire harness and operate as a 3 speed (the dash switch for the rear is 3 speed. there is no rear control).

The aftermarket rear blower motor is a Bosch single shaft, about 3" in diameter. I bet I could find one with some looking, but it's really not worth the trouble. Single speed is fine for my needs.