I just looked on Mouser.com & they only have two versions of a push/pull 500K Ohm linear taper pot & both of them are Metric (6mm shafts).
So if you want to get linear taper (better for blending in this setup, IMHO) volume pots, you might want to move the push/pull to one of the treble cut pots.
If you're fine with audio taper volumes, nevermind, but...
with audio taper volume pots the volume drops off pretty fast.
Here's a comparison:
View attachment 2975310
When wiring the pickup to the center lug it makes the taper act backwards, so you get a steep roll-off (right-hand side of graph).
With a linear taper pot, being reversed makes no difference.