Thats great. It will be ready for many more years, .... and you'll be proud to know that you're the one that fixed it up.
Ug.,Thats right, I forgot about the choke.
If you consider that your amp is pretty much a first year stereo amp, (1958 being the first year for widely available stereo sets) what everyone knew about stereo channel separation was in its infancy. The original coupling caps are of a lower value and type, and also the same channel to channel. I re-did a 1958 175-EE for a guy before Christmas and his original caps were .001 ceramic disc even though the schemo here shows .047. Then if you consider 5 years later, the type of layout magnavox put in its 8800 series (the following iteration to the 175) was very different. When an 8800 is rebuilt, people most often comment on how sweet they sound.
In the 8800 series, they often mix-matched cap values and types, channel to channel which is a contributing factor to the "sweetness." Also, in the "olden days" Bass wasn't as much of a concern.
All that said, I used an oil .1uf on the high side of each channel (the two outside tubes) and an early Sprague .050uf orange drop (.047uf is the modern equivalent) on the low side on that 175 and similar on my own 175-67 which is a 1961 model (last year for the 175). Those values stagger types and values pretty well and doesn't increase capacitance enough to need other changes. Bass is a bit increased also.
When it comes time, you mentioned the cathode resistor. When you replace it, and you should, 120ohm/5w is a good number and get a 22uf/50-100v electrolytic cap and place it on the same lugs as the cathode resistor. Tube Socket lug and ground. When you do that, you can remove all the hum pot nonsense.
