Generator Field Coil Insulation

[Conaway2]

I’m rebuilding a stock A generator and am replacing the coils because the cloth (?) insulation has deteriorated and is falling off. The coils themselves seem fine - continuity tests indicate no broken windings.

if I decided to simply re-insulate the original coils, what should I use ? They appear to have been originally wrapped with some sort of cloth friction tape.

Thanks - Jim