To be honest, I ordered them from AutoZone and they looked it up for me. The number could be in your owners manual if you have one in the glove box. AC Delco Iridium served me well in the past, so I have stuck with them. They were about $8 per plug, but as often as I change them, it really isn't bad. I run them in my Impala 3800 too.
Originally Posted By: Honda2003
Originally Posted By: Tzu
If it were me, I would keep with the AC Delco iridium considering I have basically the same truck ('00 5.3L with 251,000 miles). I put new plugs in mine at 200,000 and they will be good for 100,000 miles. Just took them all out with 50,000 miles on them and they were all clean and looked good. So they went back in and will be replaced 50,000 miles from now. I would call them worth it.
What is the part number for this plug?