Spark plug types (2002 Bonneville)
 

Has anyone been able to find the exact replacement for the "factory plugs" (AC # 41-921)? I replaced the factory ones around 100K miles even though they were still working fine. (Yeah, I broke that old rule: "If it ain't broke, don't fix it")

The owner's guide says to use that plug for a replacement, but no one had 'em. I couldn't even buy them at the dealership.

The computer database at the dealership and several auto parts stores said to use an AC #41-101 plug. The 41-101's I put in at 100K miles didn't even last 50K miles and I wonder if the difference is in the design. (The 41-921's have two opposing pointed firing tips, one on each electrode, while the 101's only have one)

Later, Joe

most run the NGK TR55's. You may or may not know that NGK actually makes the plugs for AC Delco.

NGK vs AC
 

Yep, I saw the NGK logo stamped right on the AC plug.
I paid almost 7 bucks each for AC's. Is the NGK version cheaper and is it 2-tip design?

Probably not much cheaper. A good Iridium is the replacement. Avoid Bosch on the plugs as they get eated quickly in our waste spark setup.