There's several plugs that work satisfactory.

What plug was in the engine?

You will need a resister plug. On the Champions the resistor number starts with "R". Other brands have a "R" in the number somewhere.

Mine has a RCJ7Y It's has a gasket base. I've also used the RDJ8J tapered seat plugs. The engine ran the same or at least I couldn't tell any difference... They tached the same and neither seemed to foul. The RDJ8J is smaller.

I got mine at the NAPA Auto Parts store but I had to order them. They came the next day.

Enjoy,

Jim