Need some info about spark plugs for a 440. I have a 76 440 from a motorhome with the 452 heads. The spark plugs are the 5/8 hex plugs. All the listing I find for 440's have the 13/16 hex. QUESTION NUMBER 1: Are the plugs interchangable? Can I use the 13/16 hex plugs or do I need the 5/8 hex?

This 440 is going into a truck and I have a set of headerss to fit it. It has been recommended that I use shorty header plugs with these headers so I don't burn up the plug wires. I asked the person I bought the headers from and he said his 440 had the standard size plugs in it and the boots were close to the headers, but I guess they weren't burned up So I may be fine. The only listings I can find for short plugs are Accel plugs with a 13/16 hex.

QUESTION NUMBER 2: Can anybody please provide me with part numbers I need for spark plugs to fit these 452 heads, either standard size or short.

Thanks