Bill,
What distributor are you running? I think a shielded cable is a good idea for a magnetic pickup. And don't run the distributor wire next to the alternator power wire or the coil primary wire (output from the MSD).

I like the charging characteristics of the Delco (GM) alternator, good low rpm output. But MSD even says in their FAQ that the Delco 1-wire alternators are big offenders.

1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1