I am currently running the Autolite 103's gapped at .035" in my rebuilt 355 with a cc503 cam and stock heads. I am running these plugs because I plan on running nitrous down the line. Is this going to cause problems while running NA?

 

The only problem I know of with running a colder plug is fouling. You may lose a tiny bit of power, but it won't hurt anything.

 

Agreed. I'm running TR6's until I can get my nitrous installed. If you think about it, you're not running on the nitrous nearly as much as you're running NA.