[Radioroslyn]

I took a quick look at the diagram and it looks like all of the resistors are in series with the HV. The typical set up is the B-C resistor is in parallel with HV and will have a resistor or two to divide up the bias voltages this set doesn't. No bias on the audio stages. Anyway to answer your question I would think 5 to 10wts would be plenty. A lot of times only certain sections are open you only have to replace the open ones.
GL
Terry