Converting points to a pertronix electronic ignition

Yes, your coil was hooked up wrong. You would still get spark, but the electrons would flow from the electrode to the ground tip (recall), which would quickly erode the ground tip since it is more-delicate steel that doesn't appreciate being bombarded with electrons, so check your spark plugs. Search SlantSixDan's posts for the best spark plug PN. He and others on slantsix.org site are vehement that it matters a lot. Also, make sure you remove the metal gasket on each spark plug, since you have the earlier "drool-tube" slant engine.