[exray]

I use the RadioDaze NON-RATED cloth covered wire for most everything. They sell a 600 v rated wire but it is an ungainly size. Conceivably the insulation could arc through at high voltage where wires cross or are up against a chassis. There's very few places in a radio that have more than 300 volts present. I'm sure the real world effectiveness of this particular is much higher than 300 volts even though it is not officially rated.

On the other hand, I would be skeptical about a plastic insulated wire only rated at 300 volts.