I wouldn't advice going overboard with the capacitance. Too much of it and the inrush will begin to blow fuses. Use caps that have equal or higher voltage rating than the caps you are replacing. For capacitance, get something that's in the ballpark of the old part.If the old one was, say 500uF, don't use a 1000uF cap but maybe a 470uF, 520uF, or 560uF.As for unobtanium germanium transistors. If they die replace with silicon and reconfigure the bias circuit. You probably won't notice much difference except for a huge improvement in reliability. R.G. Keen has written some good stuff about this issue concerning Thomas Organ solid-state Vox amplifiers. The good news: The information is for most parts interchangeable since you likely find a very similar design from these amps. Schematics and layouts..? Heck, if you really need them just spend a few hours to sketch them out. With these kinds of amps it's still humanly possible without a microscope and without having to spend weeks into the process. If you choose to take that path then post the sketches here (or to the Internet in general) so that in the future there actually will be some information and technical documentary about these amps to help other guys like you.
I think this would be a poor choice of metalwork for a valve/tube build.
...and the missing fuse holder may go some way to explaining why one channel isn't working.