The reservoir bottle shown above is metal.
A couple of new updates. My friend Ruedi and I worked on some of the electrics over the weekend. My clock was not working. I had it refurbed locally. I had been told my my mechanic he would have to pull the whole dash to reinstall it. When Mike Burger was here he had removed the clock in about 10 minutes by taking out the lower knee bloster, reaching up, twisting the clock, and pulling it down and out. We were able to reverse the process and reinstall the clock in about 15 minutes. This included changing some connectors to the clock. Ruedi is Swiss and it certainly helps having a “Swiss” handy when working on clocks!
Next we checked the rear fog light button and realized it worked but wouldn’t hold. A new one is on order and will be a quick fix.
Finally we looked for the rear window defogger. We had the manual out, checked the wiring diagram, looked at the wiring under the dash. No sign. Drove us nuts! Then I had the common sense to reach to Terry Conners. Problem solved. Turns out 74/75s do not have a standard defogger switch. The manual does not appear to have been updated, (I have the original manual in the car). The switch is located to the left of the shifter. All good, thanks to Mike, Terry and Ruedi.