I'll attach the schematic for the 1955 Gibson GA-9 I’m restoring. Most of the resistors test within 10%, but the 470 has drifted up to 750. It's sitting on a nice hot power tube socket, so some cook-age is not unexpected. But: Is it a grid stopper? If so, maybe a bit higher might not hurt? But these are single-ended *parallel* 6V6s -- so should their setup be as symmetrical as possible? If so, would it be bad if the drift made them more asymmetrical? Way too many things I don’t understand here. FWIW I’ve been marking up the scheme to increase readability.