[Arran]

Terry is quite right about the filament voltages, with a 50 volt tube in there and the original dropper, the series string voltage will probably be too low. This is why I usually wince when people suggested using a 50L6 in place of a 35L6 in an AC/DC set on the alternative forum, engineers in the 1930s and 40s were not stupid, if a five tube set has a 35L6 it has to have a dropping resistor as they typically used 117 volts as a "working voltage". The stories about a 110 volts as a standard power line voltage, is a myth, the only power grids that put out 110 volts were the DC ones, the AC ones were all over the place depending on where it was, what time of day, as well as the power line frequency. The 25 cycle power grids were nominally rated at 115 volts, the 60 cycle ones were nominally rated anywhere between 115 and 120, I can't remember what the 40 cycle grids were rated at but those were rare.
 If it were my set, and the candohm was shot, I would probably replace the resistors with proper sized ones and use a 35A5 again just so things aren't confused somewhere down the line. Knowing my luck if I converted it to using a 50A5, and changed the resistor values accordingly, I would forget in a few years and plug a 35A5 in there again and cook the tubes.
Regards
Arran