1999 Other Ford Model S Pinging

The vehicle is a motorhome built on the Ford V10 Triton Class A chassis and is new to me. I'm sure it wasn't maintained very well.

The pinging is a fairly loud rattle under light to moderate acceleration. My mechanic thinks it can be attributed to bad fuel or the sparks plugs. I've added an Octane Booster to the fuel and after driving 25 miles saw no improvement.

I'm concerned about changing the spark plugs because of the aluminum heads with only 4 or less threads. There are some horror stories going around about "spark plug blowout". Ford recommends not inspecting/replacing the spark plugs until 100,000 miles.

We've had the fuel and air filters replaced and the DPFE sensor was also replaced.

What do you suggest?