I have a 01' Mustang with a 3.8L V6. I am putting in an Accel Ignition Coil pack and MSD 8.5mm Super Conductor plug wires. I am wondering what the best plug I should use for that setup and what the heat range rating is on a stock spark plug originally used in the 3.8L.

 

I think the heat range on the stockers are 3 or 5. I have the same setup as you except the coil pack which i plan to add very soon, and i got NGK TR55s and they work real nice.