For a /6 with carbs.

8mm?

Magnecore?

Other?

Lots of stuff to read about this topic on the Bird Board's 911 forum: http://forums.pelicanparts.com/search.php?searchid=1639080

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It's a system.
I use MSD 6al, MSD High Vibration coil, 8.5mm Magnecore wires & NGK plugs gapped to .045-.050 (depends on how I feel that day).

I'm running a Mallory 6AL, MSD Blaster II coil, and Pertronix.

MSD box went to electrical heaven.

I use the Pertronixs also. Been using the MSD for 8-9 years without a problem, but am not attached to it. Most all of the multi-spark units will do the trick as long as they can maintain the voltage that the high voltage coils can produce.

IIRC, John Rogers measured the voltage of the MSD unit at 18K during the multi-spark phase and 36K above that to 7kish and it didn't "run out of gas" electrically speaking.

Magnecore on mine...