I run Autolite 103's (104 is stock). I also like the Motorcraft AWSF22C (AWSF32C is stock). I don't care for Champions...they're fine for lawnmowers but I don't like them in my race motor. You see very few serious racers running Champions. I've had some big name tuners warn me away from them. I've got a cross reference chart for GT-40P plugs on my website under the 'Tech Tips' section.
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Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team