[Arran]

Given that this is basically an AC radio, and not a portable with battery tubes, I wouldn't worry too much about increased B+ voltage, however I would use two silicon diodes in series in case one of them decides to short, though the worst that may happen is destroying the filter caps if it does. If extra B+ is an issue to the FM front end you could add a dropper for the FM section, however I suspect that these sets were intended to operate over a fairly wide line voltage range. Personally I would use one of those chassis mounted resistors, or use a hollow wire wound mounted on a bolt for heat dissipation. Come to think of it you could put both the tube heaters and the B+ in series with the resistor, it would help the tubes live a bit longer, the question is what is your current power line voltage?
Regards
Arran