One more thing: If you got a tach drive distributor you can convert it to twin system by taking a 6-cylinder distributor and thread the housing in a lathe to fit the tach system, you can secure it by splitting it and using a clamp over, or just a simple set-screw, then it is simple to grind the shaft to fit the drive. I would recommend th use dual pickups in one master distributor to make it more accurate, and then run the other as a slave. I made such one for a friend of mine. The distributor cap is interchangeable from 6 to 8 cylinder, no problem. This got to be a "poor-man's twin ignition" but it is simple, cost-efficient, compact and it works!! Sorry, did not take pictures of it.
If twin sparks make more hp?: Has to, because timing can be 3 degrees lower (old info from Sox and Martin), this means less counterpressure during firing / full burn. To drive the system costs nothing more than the slight electric and mechanical extra load, maybe a fraction of a hp.
Be aware that the rockers need to be slightly slimmed to fit the 2. tube (very simple job)
Thanks again,
O. Mostad