I am trying to decide which plugs I am going to install soon and I think I have narrowed it down to the Autolites. The question is should I get the 605's or the 104's? I was looking on Intense's site and they suggested using the 104's if being used on the 3800 with 6-12lbs. of boost and the 605's if running 6 or less. They also mentioned keeping the gap stock unless running nitrous which I won't ever be doing. I want to get new plugs and then a 180* thermostat so I can finally install the 3.4" pulley. Which one's should I go with?

104s are copper so you will have to pull them every oil change to ensure the gap is still in specs. The 605s are platinums and won't require the maintenance of the 104s.

Herc, every oil change is a little extreme. I would look at replacing coppers every 15k though. Platinums can last up to 60k miles, but the tip inherently holds more heat than the copper causing a hot spot. Pick your poison, both are relatively cheap.

Unless I'm mistaken, 605s are still copper, just a different heat range. Platinum Autolites (center electrode only) have an AP prefix, double platinums (center and side electrode) have APP prefix. For example: 104, AP104, APP104.

It's going to be a tough call.