i noticed the rotor button in an optispark has a very wide head on it. (head being the part the spark jumps out of and into the terminals on the cap)
it is nearly 1" or so. is there a purpose for that?
my sbc msd distributor has a much more narrow head on its rotor button.

i am planning on running a single plane with distributor in the rear. the opti up front will trigger the factory ignition coil, and the coil will feed into the rear distributor.
will the smaller rotor button head pose a problem with this setup?

 

The rotor is fixed and doesn't realign itself with ignition advance like your MSD sbc distributor does. Since rotor phasing is fixed regardless of timing the tip needs to be wider so the spark doesn't try to wander through the cap and jump to the wrong cylinder which could be catostrophic.

 

well, actually the msd distributor i have has no advance mechanism in it. it is fixed on the shaft. looking down on the rotor button, the "prong" is roughly 1/4" wide. this is the part the spark jumps from of course...

getting back to the original engineering on the opti-
i was thinking of how slack a stock timing chain can become on an LT1. when there is alot of slack, the rotor may be quite a bit advanced or retarded when the spark jumps to the opti cap, and the rotor's large prong allows it to operate correctly within a wider margin of chain slop... maybe?