comparing sizes, of either yellow top, or red top, vs a group 48 battery, a 34, or 34/78 size, is 10" L x 6 7/8 W x 7 13/16 tall at the posts. I assume 1/4 inch taller will be ok. If I get the yellow top, I might be able to do the big three upgrade, but was hoping to have it done at the stero shop that installed my system. yellow top 750 cca, 870 ca, reserve 120 capacity 55. red top 800cca, 1000ca, 100 reserve, capacity 50. This is why it is frustrating me, Some say get a normal battery, some say red top, some say yellow top. capacitor some yes, some no. If I get the optima battery, I can't get a cap right now. is the big three something easy to do, as far as getting to all of the wires? I'll have to have the car in the air, to do my fog lights anyway. AHHHHHHHHHHHHH I'm getting a headache. Thanks for all of the suggestions, chris