OK, motor's in and we start to crank it...battery's dead. So we charge it. It is a VERY small battery sold by local parts store (500 amps) After a charge it cranks the motor a few times and begins to die again. With the rebuild on the motor...we need more power but we can't find a battery to fit. I took a tape measure to the parts store and all the batteries with enough amps (750 or more...) are 6.5 in. the space in my midget is 6.25 in between the lip of the hood and the heater box. What am I missing? DO I need something special? where do you get them and am I gonna have to shell out another $200 to get it? or is 500amps all I'm gonna get?