The tachometer output should go to the tach not the alternator in my belief.
May I suggest that you call Petronix as they most likely have a customer help line.
Here is a link to their instructions: http://pertronix.com/support/manuals/pdf/rev.pdf
Here is a link that you also may find helpfull: http://www.pertronix.com/default.aspx
Here is their phone numbers and address:
PerTronix, Inc.
440 East Arrow Highway
San Dimas, CA 91773
Phone: (909) 599-5955
Fax: (909) 599-6424
Hope this helps.