Spark Plug Recommendation

[sdcbowler]

Have searched the web for info on which plugs I should use, but have not found the answer. 413 CID (not a Max Wedge), both heads are 4006452. I don't know what vehicle the engine came from but it was either a truck or a Motorhome. Summit Racing site says the Autolite ATL-85 will fit. All recommended plugs from the site have a .375" reach.

Any Suggestions from the forum will be appreciated.
Thanks

 

[Chryco Psycho]

Champion RJ12 YC or Autolite with equal application