x3 on the 123.
I did manage to source a NOS vacuum cell for the very similar Bosch distributor in my '71 Volkswagen last year, so they are still around here and there. The old one was frozen as well. The person I bought it from has several more - but there are subtle differences so the spec/specific type is important. Once installed, the car ran much better (duh!).
You will undoubtedly notice a marked improvement once you have the additional advance in your Pagoda.