I just found that cover on another sale board also. I found a lot of dual distributor setups, so that would support the 12 spark plugs. Seems the museum piece may be showing incomplete parts.
To answer your question, it seems the t is already there to exploit TJI, if I understand the system correctly.
That would be it then. If one mag went down the engine would still run. I was thinking on it, and seem to remember something (Fire engine??) that had coil ignition and a mag. Before my time, but still 'talked about' when I was a kid.
This came up on google. Dennis.
Belongs in the ugly section though