For 25 years I drove a 1970 Cougar XR7 351 Cleveland with A/C. There was a lot of motor in a small space and changing the plugs was a knucle busting experience. The recommendation from the dealer was to lift the engine as much as possible with a chain or strap wrapped around the engine without loosening anything. I took it to the dealer a couple of times and the mechanics swore everytime they had to change the plugs, so eventually began doing it myself. I’d usually change them once per year (it was only a summer car that was driven 2K), did it without lifting anything, but it took a long time to accomplish the change. The plugs were small and in very hard to get to places that you usually had to feel your way around to find the hole.