I really like the Accel C-cut spark plugs and use them in my Pontiac 455 street pump gas engine #0437S.
They have been in there since March 2021 and have not fouled out any even when the tune was off early on.
Now that Pontiac 455 is Dialed in perfect to my liking the Accel C-cuts stay perfectly clean all the time even on cold engine starts warming the engine up .
I bought a set of Accel C-cuts for the 1999 Chevy Tahoe 350 ci Votech V8 and they are performing excellent too.
The 1987 Corvette I am using NGK Copper Core spark plugs yet, Accel makes C-cuts for my Vette engine but for some reason they are extremely expensive at $65 a set of 8 been holding off buying them because I don't drive the Corvette much at all in 2021 year.
Accel C-cuts are a perfect match I have found for Heat Range for todays 87-93 pump gas engines stock or custom built as we do here on Grumpy's place.
If You have A Factory Pontiac RAIV Engine like I have yet, a L-88 427, 1970 LS6 454 They require a Cold Heat Range Spark Plug and need 110 motor octane gas pure uncut 100% of the time or switch to E85 Fuel to operate correct no detonation.
Accel C-cuts are too hot for these Factory Race Engines.
NGK Copper Core Racing Spark plugs are a better match and ones to use now for them.