What Alan said. The Optima in the 34/78 BCI size, which is what fits most of the 12 volt trucks, is slightly larger around the top perimeter than a standard battery. The stock hold down can be tweeked to fit, however. Just slightly spread the sides of the top frame out a bit. The trucks that use the cross bar type hold down should be ok wiht no mods.
While the Optimas are the best on the market, there is one precaution to charging them. You can not "fast charge" them. They have to be charged slow.
As far as how tough they are-I saw a demonstration once where they shot a hole through the battery with a .357 Magnum, then put it into a car and started it! That sold me on one.
