spark plug type for 351E

[dean351E]

What kind of spark plugs are you using for the 351E (1966 GMC 2500 in my case)? The manual calls for an AC C44NS which far as I can tell is no longer produced. The auto parts store cross-referenced this to a Champion RN14YC (also called type 405) but in what little I've been able to find online I've also seen an RN11YC specified. I know the difference is heat range, but is that a 3-plug difference in heat range? Which one is ideal? What are typical plugs used for this application today?

[TJ's GMC]

I use NGK plugs in my 305E...I'll get some numbers for ya.

[Clyde]

I used NGK Iridium from Advance Auto #6637 in my 1966 GMC 3/4T Pickup with a 351 V6.