I've installed many MSD boxes on cars using stock ignition components, I can't recall one premature failure of any part. I had a 6AL installed on my Sunbird and Skyhawk for about 2 years before I did an engine swap to an engine with DIS, never experienced any premature failure of ignition components.About your experiance, the first thing that comes to mind is poor grounding of the coil, the next thing is something wrong with the components used. Many people, myself included have used MSD boxes on in cap HEI coils without issue.