I would use the largest size that will fit that you can find at a local retailer with a good warranty. I alway used AMG's in my off road vehicles due to the extreme angles and there is no doubt that they are superior, but in my everyday drivers, I just use Duralast Golds or WalMart Everstarts due to price, warranty, and availability. I have had good luck with Optima batteries but there are two things that I would caution you about. #1 is that they seem to discharge more if they sit for a long time. #2 is that they tend to not sell as fast and if you buy one at your local parts store, it may have been sitting in a warehouse or on their shelf for a long time. Other than that, great tips from the other guys on here about how to fit the largest possible battery.