[JimL78]

I always ran AC 43N sparkplugs in my L78. I couldn't find them when I went to get my car last year so I put the equivalent Autolights in it. Thought that was sacrilegious putting Ford plugs in a Chevrolet. Over the winter I found some NGK plugs that look identical to the 43N. They are B7ES. The heat range seven doesn't have the projected tip like the fives do. Maybe you could use the seven heat range in the shorter plug and it will match up to the old ACs.
Jim