You need to expand your horizons a bit. Champion RV8C is the right spark plug.
There is no exact Autolite cross ref for this plug.
Plugs are WET.. you have a carb fuel control issue...flooding,fuel pressure.needle seats fuel filter etc.,
there is a big difference between WET plugs and plugs that are a little on the cold side.
and or a ignition system fault. Cap coil wires etc..
But the RV8C plugs are the right plug for the job.
any auto parts store will have them.