Well this is really a Mopar site but in general do the usual things. Make sure the points are correct, wires clean and tight, rotor and cap not corroded. Try to trace where you last had spark. At the points, from the coil etc. Then you can look further down the line to try and troubleshoot. For example if there is spark coming out of the coil you know the problem is in distribution. Cap, rotor, wires etc. Make sure your grounds are good and the battery fully charged If the wiring is original there could be a broken wire in the harness or in the distributor. Many new offshore made parts are bad from the box as well. I don't know what else you have changed recently if anything. Also lastly make sure you replaced the plugs gapped correctly and also firing order is correct.
You might also want to post here:
https://forums.aaca.org/?_fromLogin=1
They have make specific forums as well as a lot of smart experienced people as well who might be more familiar with Pontiacs.