First things first, before you go blindly replacing a battery, have it tested first. Some random person telling her she needs a new battery is meaningless. Neither you nor I know why the battery was dead so test it before replacing it.
As far as what battery will fit... Any autoparts store will look up the vehicle year/make/model and give you the correctly sized battery. You can't just buy whats on sale. A group 65 battery may not fit a ranger, but since your post doesn't say what year/make/model truck your wife is driving, we'll never know. The listed size is a group 58 battery. A group 65 battery is taller and wider.
Last edited by FireRanger; 02-11-2011 at 08:23 AM.