Re: What pickup did Metallica use before EMG??
James used an Invader in his Flying V copy. In his Gibson Explorer he may have just used the stock Gibson pickups, I think I've read somewhere they were Gibson 500Ts. Can't say I've read a reliable source yet claiming James used Distortions.
Kirk probably used stock Gibson pickups in his Gibson Flying V. He started experimenting with different pickups during the Ride The Lightning tour, including Duncan Distortions.
So, if you want to get as close as possible for pre-EMG Metallica, an Invader or 500T in the bridge would be your ticket. A Custom or Distortion would be good also.