Figure give it a week add them up and see what we get. So far the consensus is on the older ones. Be interesting to see what serial number they started messing up around.
endurance problems went back to the beginning.
John Soemer told me the 505 and then the new 6 series generally they ran with two boxes. Unp[lug one and plu imn the other and keep racing. Take the dead one and send it back to Autotronics who fixed them for nothing or very little cost. When I gave up on the MP Chrome box, I bought the 6T figuing it would be more durable. Whether that did it, or the rubber mounts that came with it, or they had figured out the failure points I don't know. Hasn't failed yet.
There's more. Look at theAutortronics MSD 6 instructions I've posted. MSD 6 series came with insulating tabs and jumpers so the owner could quickly switch back to the original system if there was a problem. I bought that around 1990. So even then Autotronics was aware of the problems/concerns and had a solution.
Only MSD unit I've had to send back was the adjustable timing box.