No. Leave R51 (33k) as it is.
C- comes from the junction of R51 and C33, same as it does now.
R52 (22k) gets replaced with a 10k fixed resistor and a 25k pot in series
or for a less touchy adjustment, use an 18k fixed resistor and a 10k pot,
20k resistor + 5k pot would also work. Even less touchy, but less adjustment range too.
the idea is that you want something that adds up to about 22k between a fixed resistor and 1/2 the pot travel.
basically the pot ends up controlling current flow and thus voltage drop through R51. If the pot dies, you get no voltage drop, so the tube grids get -26 instead of a situation where you get no bias and the tubes fry. I just happen to like that setup better because I've had problems with old pots getting crusty and losing connection while adjusting bias before. Not a lot of fun trying to adjust the bias on something and suddenly your brand new output tube set flashes bright red because the pot hit a dead spot.