[Dave at Pelican Parts]

What you're checking when you put the tach on the center coil wire is every spark. So you will probably see a mish-mash of four images, only one of which will have the timing mark in (or near) it. It sounds like that is good enough to let you set the timing.

Are you getting a spark on the #1 cylinders? If so, then keep monkeying with the clip-on lead until you get a reading...

Not sure on the tach. Try disconnecting the stock tach when using the Sears one. That will eliminate one possible source of problems.

--DD