You can't discuss the optimum loading for a cartridge without knowing the capacitance and inductance of the tonearm cable. Some very expensive tonearm cables have inductance that is a significant factor or capacitance that is a significant factor in the frequency response of the system. They may give subjectively a pleasant sound, but IMHO depart significantly from neutral.
If you know the specs for the cartridge and tonearm internal wiring plus tonearm cable, you can easily calculate using the calculators provided by Hagerman here:
Not 47K ohms Jerry. My Minimax phono stage has two options only for MC, 100 ohms and 47 ohms. I wouldn't have believed 47 ohms would sound better to me till I tried it. More body on vocals, and less sibilants. Overall, very pleasing to the ears. I tried it back a forth a few times to make sure I wasn't just imagining.
Anyway, been a couple of months. I am very happy with this setup. It is the default vinyl playing instrument in my system until I get the cart swap for the Bergmann.