Replacement Battery for '05 GTO
To clarify some alternatives to the Optima or the AC Delco stock part, you can get a Duralast Gold "35-DLG" from Autozone, $90 (Item #115788). It has an 8 year pro-rated warranty and a 36-month free replacement. It fits well enough, a little tight by the fuse box, and have to squeeze it in to get the holding bracket back on the bottom of the battery. I just installed on my '05.