I might have found my "coil" problem, which may well not be the reason I have no spark.
Not being able to identify the flywheel I had -- the CDI type or the MDI type (see above) -- I was ready to "bite the bullet" and just buy a new ASAM conversion kit so I was sure that the coils and flywheel were compatible.
Before doing that, I wanted to make sure I could actually get the old flywheel off, so I finally pulled the engine from the Yazoo frame (took all of 20 min), got it up on the bench and pulled the flywheel.
One thing I noticed right away is that the legacy flywheel has two grooves in it that accept two corresponding ears from the fan and position it (see pics). Can anyone identify this as a CDI flywheel?
From the he ASAM conversion flywheel pics from OPE, there are no such grooves on the MDI flywheel, so I figured I would have to get out the grinder and lope off those ears on the fan to get it to seat properly on the flywheel (the fan also had two dowels on it to help with alignment so I wasn't too concerned about this mod).
However, before I took the grinder to the fan, I thought to myself "hey what happened to the key positioning the flywheel on the crank? I don't remember seeing it, did it pop off when we pulled the flywheel?" So I went back to the bench looking around for it and found it -- in two pieces. It had sheared: one piece was in the flywheel and the other in the crank.
When I finally reached that old country mechanic who sold me the Yazoo about whether he had upgraded the coils, he mentioned that this could happen, and he said to check the key as they can shear and throw off the timing of the ignition. Sometimes nothing beats experience.
So I am getting a new key, putting it all back together and seeing what happens.
Stay tuned.