The DieHard has been a JCI battery since 1965, wiht the exeption of late '94-'97, when it was manufactured by Exide. Unfortunatly, Exide manufactures an inferior product, which cost them the contract.
If you're looking fo an AGM battery in a DieHard, take a look at the DieHard Platinum, manufactured by EnerSys, wh manufactures military and industrial batteries. I've put in a few, and they are an exellent battery. I will admit, there are some fitment issues with hold downs that will need addressed, but nothing that can't be easily taken care of.
Personally, I'm running an Optima group 78/34 that came from Sears, didn't have an issue in the 4 years it was in the truck until a few months ago. The truck had sat for some time, and it drained down, had to get it warranteed. But when the truck was used regularly, it always started it, even if it was run down.
