Personally I'd fit 500k pots. Various forums talk about the Ric 330k pot having a measured value that's normally just below 500k, so maybe their agreement with CTS was to badge up 500k pots that measured slightly below 500k with their '330k' part number (also to put people off mimicking their circuit, so copies using real 330k pots have a lower value than Ric use)?

It makes sense to me to use 500k pots because the way Ric wire their control circuits, the two volume pots are always in parallel and so the pickups always see a 250k resistance to ground. It's like wiring a 500k resistor across a 500k pot to get a 250k pot.

Real 330k pots would have an equivalent resistance of 165k ohms, which is low, even for a single coil, and would knock off a lot of treble.

I think I've said elsewhere that I fitted 1 Meg volume pots in a Ric 650D (mini humbuckers) that had 250k pots, and got all the missing jangle back.