The Pertronix is a HEI style unit. It is designed for those who want their Dizzy to look original. But from what you have done, that's not you.
It will ALWAYS be better to go with GM products. I.E. AC DELCO, etc. So if you want HEI, do the mod described within 6066GMCCLUB.
Contact member Rod Johnson, he makes the parts and will instruct.
WE7X@AOL.com
See our TIP section:
http://6066gmcguy.com/hei.html Pete Chronis has done this as you will see.
PS, nothing wrong with points ignition. However, point-less should last longer. It is a better idea and possible performance upgrade.
Modification baseline:
New/reman Delco HEI Distributor $108. 1979 Buick 231 Cu in. Unless there is something about a Magnum that prevents this. Jolly says the 351 Magnum was introduced in 1966.