1966 318 2 BBL Poly spark plugs

hello all;

I am chasing down a vibration/resonation in my 66 Coronet (stock engine) and I am going to change out the spark plugs in case it is a misfire.
Anyone have recommendations on the best spark plugs application for this old girl ?
Thanks

It came with Champions. That's what I would use. 63's are what's listed. More Information for CHAMPION 63

Someone on here said NGK number 5 was the correct plug.
My manual treats plug numbers a secret. Says look on tne door post. Nothing about plugs there. Two auto stores show a number 4 as the correct plug. They have lots of number 4 plugs, hardly any number 5 plugs. If NGK is using the same heat grading as they do with motorcycle plugs, then a 4 or a 5 is a fairly hot plug. Any thoughts on the subject from other owners. I have a 318 in my camper van.

Welcome. I just pick up a set for my 64 fury 318 poly. #63