You can put a slightly larger battery by 1 inch longer a Group 34
And a battery that sits a lot should be charged by a battery charger once a month at least unless you have a larger drain on it by other accessories pulling to much power and draining a battery. Also a battery that has has drained to nothing may not come back to being a reliable battery or work properly you might get away with it if use it everyday but if it sits a few days it may give you problems so to realy test a battery let it sit a weak and do a load test
A Group 78 is a side post unless it also has top posts
![]()