Spark at coil and distributor but no spark after plugs installed and crank at key

Best way to verify proper sparking is to remove the distributor and spin it by hand with key in "run" and viewing for spark on a "spark tester". Best to wire from the coil HV wire straight to the tester, which can be a spark plug with its body grounded to BATT- or just the metal wire tip held close to a bare bolt on the engine. As a further "bench test", flash a timing lamp (pickup clamped over HV wire) at the distributor's reluctor wheel (distributor cap off). You should see the pickup teeth aligned when it flashes. BTW, same basic checks if changing to a GM HEI module, especially to check the polarity of the pickup wires is correct. For those w/ an old points distributor, ground the body of the distributor with a jumper wire.

I wonder if you can view the "pickup teeth" (or such) in a Pertronix under-cap. Perhaps they are nice enough to provide alignment marks. Going even further, some people drill a hole in an old distributor cap at tower #1 to verify w/ timing lamp that the spark occurs when the rotor tip aligns with the tower, termed "phasing". Of course you need to have the engine running, or at least cranking, to verify this. Chevy guys can even buy a transparent cap. You can find youtubes for most of this.

As 67Dart273 stated, also check that the Pertronix gets IGN power both with key in "crank" and in "run". That is a common issue when retrofitting, and even in the OE ignition if the ballast resistor gets broken.