Also check that the thing is not overcharging. We just had a recent war over this LOL Is the ECU mounted in the stock location? If so, it should not be particularly victim to engine heat. There is a possibility that a coil with a primary partial short could be drawing enough extra current to damage them. Might pay to replace the coil
The poor fact is, that obtaining quality parts for these is nil. Even if you get "NOS" they might be a problem with bad / deteriorating components, particularly capacitors.
Some of us use GM HEI modules, and a few guys have even gutten a Mopar box and put the GM module inside