Dale RN55 are fine. The RN series are all de rated being mil spec vs the Industrial CMF range. A RN55 is 1/8w vs a CMF55 which is 1/2w, yet both are physically identical in size.
They are also rated by tolerance, 1% being the norm, but .5% and .1% are also available at a higher cost. Personally i would buy a bunch of 1% for the same cost and measure them myself, but 1% tolerance is perfectly fine for a volume control, you will never hear the difference. Finally there is a temperature coefficient, 25ppm, 50ppm, 100ppm, the lower the better, but again irrelevant for a volume control so just stick to the basic 100 or 50.
Finally, what resistance values to use. Goldpoint have charts on their website which are a good starting point
https://www.goldpt.com/r_series.html ..don't forget to double up when ordering as you have a left and right channel to build.
I have built a few vintage Goldpoint stepped ladder attenuators that have 96 resistors on them, the novelty wore off fairly quickly
