[Arran]

Even if it were only a case of bad tube sockets you can still buy brand new 4, 5, and 6 pin sockets from several sources, usually made out of porcelain but there are Bakelite ones out there to. The mods were obviously done because there was a major failure like a shorted filter cap, probably the output filter cap, I don't think the fact that the choke, original speaker, and bias resistor were all removed was just because someone had some time on their hands. In the case of a 90 cathedral it is also a fairly collectable set, we aren't talking about a 1960s AA5 clock radio where nobody cares whether you hack it up or not.
Regards
Arran