[Arran]

 Winding resistances are generally higher for 25 cycle transformers, double or more would make some sense given that the core is larger and the frequency it's designed for is less then half. You can check resistances but the best way to know is everything is right is to yank the tubes, and apply power to the transformer, assuming that there are no obvious dead shorts across one of the secondary windings from exposed wires or a shorted pilot  lamp socket, etc. In my experience 25 CPS power transformers work fine on 60 cps, the secondary resistances may be higher but so is the primary, what matters is the ratio between the primary and the secondaries.
Regards
Arran