I doubt that your head gasket problem was a direct result of the ELC.
I have been running Texaco PreMix ELC since late 1998 and almost 100,000 miles on it.
Texaco Engineers informed me that the only problem they had during introduction period were to an oring on the backside of cylinder liners on N14 adn M11 trucks that had in excess of 750,000 on them. Total number of trucks with a problem was about 12. Series B engines use a parent block and do not contain these orings.
Cummins Fleetrite Division at the time did not have a competing coolant and having read their letter, talked with Cummins Tech Line reps (very vague answers as to what to check on my 96 truck even though they said they had trucks which had a problem they could not tell me exactly what might be affected by the coolant - at the time I had 30K on the coolant), having talked with Texaco Engineers at the Int'l Workboat show two consecutive years, and then seeing all the engine OEM's offer the same product as private labelled factory fills the third year, I feel very confident running the ELC fluid. (Detroit, John Deere, Cummins, International, Caterpillar, Volvo, all now offer ELC branded coolants)
It has been through some of the hottest weather in Houston (+100 with high humidity) and run cooler than the green silicate product did the first year and half.
I also had white deposits forming in the rad tank FROM the FACTORY COOLANT FILL prior to changing to the ELC. Noticed this tracking down the elusive "over active coolant gauge readings" caused by the poorly designed thermostat (which has finally been updated).
This deposit / solder bloom was growing at the solder joint of the tank to the core. It has not progressed any more since using the ELC.
Good stuff but I went with the premix version rather than the concentrate that you then mix with tap water. Tap water varies quite abit and wanted no excuses from Texaco if it was not up to snuff in performance. Had to order it from an industrial lube supplier.