AC30 Grounding Rework

I have built my own 300b amp, and obviously spent a while considering the grounding.
I have just been given an AC30 to repair, and have done so, but am appalled at the grounding approach and associated noise.
I was just wondering if anyone had rerouted the earthing on an AC30 to reduce noise, including isolating signal and chassis earthing, and what their experience had been?
Many thanks