Check Tom Langdon for the HEI distributor. I prefer it over the Pertronix because if you have a part failure and you're on the road, you can get replacement parts for the HEI distributor. Where will you find a replacement Pertronix. The alternative to a failed Pertronix unit is to stick your old points pieces back in.
If I remember correctly, the Landon distributor is a S-10 unit. I've already replaced one part in mine without any problems.