I've got a 84 5ks. Anyone on the esteemed list know the largest battery that will fit? It's under the back seat. The (frozen) one that's in there now is a 5-year-old group 41 Exide, no vent. It was -29C today...brrr. Also, is the thermotime switch on my '82 Coupe likely the same one that's malfuctioning on the '84? Will they swap? TIA, Steve Bigelow Ottawa ON 84 5ks 82 coupe