In your case, don't get hooked to any one brand of plug. That series of plug (J series in a Champion) with the short reach like that has a very limited selection of plugs. Cross reference charts and tables are almost worthless to try and find a plug.
My best guess without knowing more is you need at a minimum of a Champion 12 heat range to start. Maybe a 15, but you can't get that in a Champion.
So...if you take what you have a do a little tuning first it will be easier to see what you have going on.
The thing is DEAD RICH at idle and cruise, and from what I can see, it looks like you need more initial timing and more total.
Once you start getting a cleaner plug, it will be easier to see heat range.
And again, you may end up with an Autolite or something to find the correct heat range. You may need something in between what NGK offers and someone else may fill that hole. Sometimes when your plus selection is limited you have to buy what makes the engine happy.
Feed the dog what it wants to eat.
BTW, what carb are you running?
