Have you ever open the engine lid on a 911? Not a lot of room in there to work on things!
Not so fast, Grasshopper! You forgot to say "new" 911. If you open the engine lid on an early air-cooled 911 you will see a couple Weber carbs, and... not much else. The engine was very clearly exposed on a 911. Before watermelons (green on the outside, red on the inside) took over the automotive industry and without anyone ever being asked declared the exhaust fumes coming out must be cleaner than the air coming in. (True- allowable exhaust particulates are lower than the air in many places.) Now thanks to computer aided design hardly a cubic inch of engine bay space is wasted- its all used to meet regulatory requirements. Not only Porsche. Try and find any carmaker today with an engine you can just reach in and put your hands on.
Now I don’t know about Spectron but if you were a smart and discerning audiophile and bought a quality tube amp then odds are you will find plenty of room in there and it would be no problem to replace that binding post. Not that it would have broken off in the first place. Tube gear tends to be made to last. Digital ages in dog years.