Dave

Faster and easier for you to simply buy the one-size Heli-Coil set (based on the stud's original Metric thread size). If it's your first time working with Heli-Coils, then you're going to bust up 3-5 coils trying to get the first one installed correctly anyway. 

I always look on eBay for a used set that someone worked with 1 time. You can buy the coils separately on Amazon or pick them up at a LAPS.

The key to the whole problem is to know the thread's diameter and pitch at the base of the stud. 

It is well known that both the carb Needles and Needle Jets need replacing every 10 years (or so), due to the hammering effect that air moving across the venturi of the carb has on those 2 parts. If your Needles are 40 years old, then it's no wonder you're getting a "rich" reading on your plugs. Those 4 carb parts have simply been "hammered" into a larger opening size which allows more fuel in.

Dave

The measured resistance of the correct plug wires should be zero, nill, none, nada.

Also, the bike starts up really well. Full choke - hit the starter - fires up in 1-2 seconds. Tells me my Dyna III is putting out a good amount of power.

The question was not, "Does the Dyna have good spark ?" The question is, "When does it spark ?"

I’m glad we made this connection though.