Adjusting pickup gain level

I'm servicing my amp and will soon check the bias levels, as described in the service manual. I wonder also about the pickup levels, I have the correct cartridge but not sure if perhaps someone has fiddled with it over the years. The manual refers to a Rockola test record that should be used to adjust the input level. I take it these are rarer than hens teeth? Anyone have any other tips for tweaking / testing the input other than hearing it?

They way I set them up:

1) With both gain pots at approx midpoint, play a bit of a loud record and swap it with a low record. With AGC on both should be reasonably close in loudness.

2) Shut off the agc (put it in test position). Play a mono record and check for balance (leave balance control centered). Turn AGC back on an listen to several records of varying levels.

During rebuild of the tube amp in a GP160 I had used a generator to set up the tracking accurately, but later changed the preamp I'd added and was too lazy to pull the amp and PSU out, so I just did it by the method I described. The models that used thermistors could really only be setup by listening.

Rob/NYC