"The 'R' I was referring to was for the AC plugs which you said was R44/R45..."
That was "ta man" that posted the the R44/R45 numbers.
"...The reach is 3/8" for the 6x (all stock heads) I believe.
The .460" reach is for the Ehead type of heads..."
Well, I suppose you could be correct. BUT, I've been lookin up plug info for 2 days. The most popular reach is .460.
https://www.summitracing.com/search/...tOrder=Default
Butler shows that the E-heads require 3/4" reach plugs.
https://butlerperformance.com/c-1291...num-heads.html