I've actually heard to not run E3's... not only are they expensive, but some claim that they are much more likely to drop the ground electrode from vibration.
I just run NGK coppers. Never had a problem with any of NGK's products.
Bottom line is the engine will run much better on fresh plugs than ones that are completel worn out. So Motorcraft, AC Delco, NGK, Bosch, and possibly a couple others that I forgot.
If you do go to some fancy platinum or iridium plugs, be sure to put a dab of anti-seize on the threads, since they will last a lot longer than the standard copper types. Since they'll be in there for a long time, you don't want it to be difficult to remove them 100,000 miles later...
1996 Ranger 3.0, 5 speed stick, 4x4, 3.73's, 31" BFG AT KO's
Wiring, it's all fun and games until you poke yer eye out with a soldering iron...