Quote:

stock big block iron 3/8"

stock small block iron 3/8" Nope, all the stock L.A SB heads use 3/4 reach plugs

stock HEMI ???? my aaftermarket alum heads use 3/4" not sure about stock cast iron? I guess also 3/4"?

Aluminum aftermarket Big Block 3/4"

Aluminum aftermarket small block 3/4"

is the above correct?

Nope, see the SB quote correction above, 426 Hemi uses 3/4 reach plugs also like the L.A. SB Mopars use

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)