[jpnovak]

Correct. The 964/993 distributor rotates CW. The SC rotates CCW. You can not turn the 964/993 distributor backwards because there is a weighted advance phasing mechanism that rotates the rotor to keep the tip aligned with contacts as engine speed and timing advance requirements change. Simply changing the distributor timing gear does not work because the weights swing outward on their pivots when turning the wrong direction.

JB Racing makes one.

I had some parts to convert SC/3.2/930 distributors to twin plug but am currently sold out. You need an adapter ring to hold the twin plug cap and an adapter pin to put a twin plug rotor on the existing shaft. This only works well where you are using some external crank pickup for timing.