With the C2A, you have the volume and balance pots stuck together, so in some ways it's actually easier to install since the 75K resistors can just jump from the balance to the volume pot. I would go for something with long leads for the 75K resistor like an RN55D. May as well use the same for the 33K I suppose.
If you're going to spend $300 on four resistors, you may as well just throw the attenuator upgrade in, as it will provide very good channel balance at low volumes.