[JimMac53]

The original, per the schematic you posted, is just a single gang pot with a tap. I don't see anyway to mimic the original pot with a dual gang pot, but maybe someone else has a nifty way of doing this.

If it was mine, I'd use a single gang 1 meg pot and leave the connection to tap unconnected. You'll lose the loudness contour which is effective at low volumes, but the tone controls can restore most of this.