I would also consider moving at least one of those cans underneath to the location on top where the silver one is. Lots of heat in these things. That big brown resistor connected to the one gets toasty hot, and being connected like that it dumps heat right into the cap. I used a chassis mounted one in mine and landed the wire at the end of a terminal strip, with another wire from that point to the first cap. The heat goes into the chassis instead of just baking all of the parts right around it, and its isolated from the caps by 6" or so of wire. That entire area on mine is very obviously toasted from the old resistor, the transformer leads are very brittle. The char marks on yours are pretty obvious as well.
I had to replace the bias and balance pots in mine. the originals would randomly drop out when adjusting and the tubes would lose bias. I did not re-design the bias network to make it fail-safe but at some point I plan to get in there and do that. I've got a schematic somewhere from
@dcgillespie that includes that as part of the tweaks. I think your pots may have been replaced, at least they don't look as crusty as mine did. At a bare minimum they need a good cleaning.
something else I did was to remove the old rivets that are used as bias test points and install tip jacks. Makes it easier to set things, just plug the test probes in and make adjustments rather than trying to hold two probes onto two different rivets at once with one hand while using a screwdriver in the other hand.
Many (most) of the carbon resistors in mine were off-value. Honestly I'd probably suggest changing all of them, or at least measure. That screws up performance and they tend to be very noisy as well.
Power switch is easy, depending on what you want to do. I removed one of the aux outlets and installed a slide switch that fit the hole and existing screws. Its not my favorite type of power switch but it was minimally invasive and required no modifications to the amp chassis. The bad thing is I have to reach around the back of the amp to turn it on.
Speaker terminals are common for the era. One of mine was broken and now its got a set of dual binding posts in that opening. Also done without any mods to the chassis beyond drilling out the rivets that held the old terminal board. I connected my jacks to the 8 ohm terminal. The 16 ohm lead needs to be landed somewhere inside though since the feedback connects to it. Thats the resistor with the small cap on it going from the 16 ohm terminal to the single terminal strip with the yellow wire on it. I think I mounted a single terminal strip on each side using a screw through one of the old rivet holes to land the 16 ohm transformer lead on, and the resistor ran from that spot.
These are nice amps, but they honestly suck to work on. Very cramped and the layout doesn't help any.
