Will these plugs work?

[Mudman]

Hey guys, today I went around looking for autolites but couldn't find any in the right heat range. So I was trying to talk to the napa guy about the copper core champions we use. He said he didn't see them marked as "RN11YC4" so he gave me these (which he said was equivalent). I'm skeptical at best, the number for these champions are RJ8C. Anybody heard of or used these before? I'm guessing the 8 means they're pretty cold plugs. I'm running 15psi. Will these plugs work for me?

Thanks!
Zach.

[1966 dart wagon]

What is wrong with stock heat range champions? there are plenty of guys using stock champions and making 15psi without issues, are you having issues which is swaying you from using stock plugs?

[Mudman]

I just wanted to go one range cooler than stock to keep down detonation. Our premium here is only 91 octane and I just wanted to play it on the safe side with the slightly upped boost. That's all. But I feel that these plugs I was given will be too cold, I was just wondering if anybody knew about them.