You can use a 50B5 in place of 35B5. This substitution will cause the radio to come on slower but increase filament life.
In your radio a 12BA6 could be substitued by tubes like 12BD6 and 6BJ6. (6BJ6 has a 6.3 volt filament but will work as tubes are wired in series.) 12BO6 doesn't exist. "O" is not used in tube numbers as it can be confused with Zero.
Where do the other ends of the wires connect? Do you have an antenna coil or loop in your radio? If the radio had a loop antenna it may have been removed.
Norm
: On the left/rear of the chassis (underneath) there is a "terminal strip" with red, green and black wires connected to it, but not connected to anything else. The wires are approx. 5 inches long, and appear to have been cut on the ends not connected to the strip. Any idea what these wires should be connected to? Also, can a 12BO6 tube be used to replace a 12BA6 tube? Are there any tubes that can be substituted for a 35B5 tube. I've checked the tube substitution page on this web site, and it shows no subtitutions for the 35B5. Any assistance would be greatly appreciated.