Back when I had my '71 Hemi Charger R/T, I had very little problem doing that plug - I'd put fresh plugs in every spring. PDB car. Different models & years MUST have had different clearances, because mine was not that difficult.

Now I had a buddy with a 1969 Mach 1 with a 390 & there was at least one plug where you had to jack the engine up several inches to get at one of the plugs. That would get old real fast! That engine was shoehorned in.