Another battery option, for cost savings if you do not want to/can't do the modifications to fit the Group 31's. If you have an Interstate Battery Truck, or Interstate Battery Store (One of the actual Interstate Storefronts, that only sell betteries, not an auto parts store that sells Interstate Batteries) they have the option I have gone with 3 times now. The have a stock size battery that is all black. No markings, no labels, nothing.... just a black battery with 2 posts and a handle. I have heard them called "blems" or reconditioned batteries (On the receipt they are listed as ECONO AUTO). I have bought a total of 5 now. A set of 2 4 years ago for the 6.0 Excursion, a single for my 98 Sable Wagon, and now another set of 2 for the Excursion this past Saturday. 4 years on any batteries in a 6.0 is a really good lifespan, the 6.0 is ******* batteries. I have read some guys are happy if they get 2 years from a set. These batteries are (at my local store in the East Side of Indianapolis) $39.95 + Tax. For 2 batteries, plus a core charge for the 2 batteries was $121.87 out the door (I had the family and was driving the truck, that is why I went the core/return route). The core refund was $36.38. So 2 factory sized batteries were $85.49. The only "thing" about these batteries is they only have a 30 DAY warranty. However, I have found for the most part, if the battery doesn't fail in the first 30 days, it is more than likely going to be OK, for the "long term". So if in 90 days it dies, it is $40 for a new battery.... but I can't justify paying $125 + each battery to get a warranty that will give me 20 bucks off the next battery in a few years. I can buy 2 or 3 sets (4 or 6 total batteries) of the ECONO batteries for the same price a 1 set (2 total batteries) of a "name brand" with a warranty. Just an option. I have been pleased with them, and have no plans on buying any other type of battery unless I don't have a choice. (They don't carry every battery option in the ECONO, but have most of the popular sizes). Talking to them, they sell a TON of ECONO pickup batteries, a lot of fleets are going to them.....