2008 3500, I know in past research I found out there is a different battery group you can use in place of a 65 but for the life of me I can’t find that info again. Just ordered the ce electric cable kit and will be doing new batteries at the same time. I’ve got 6 years on theses interstates and now I’ve moved to a more extreme climate so figuring now is the time to fix it all correctly.

 

I know from having Fords with group 65's that nothing else fits easily. They do tend to be a good value for their CCA.

Group 31 is taller, also a bit skinnier. It's what fits my 90-93 dodges (factory) so I'm reluctant to change even though I usually face a price-premium for the size.

 

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Group 65 is actually a great battery for range of cca/ah ratings, and availability.
group 31 won’t fit in place of a 65, most height/length issues. In the first and second gen you could use 31’s all day long, with only mild modifications to the battery trays.

if you are buying group 31. Buy them from a class 8 truck dealer. Those batteries are considered consumables for those guys, as every truck has at least 4, and service departments go through pallets of them.

 

That's good to know, but none of those around here. Interstate from the local parts store it is.

I'm looking to place my batts elsewhere, so I can be more flexible about the group size.