Ok, here's the situation...

I have an electric golf kart that is 36 volt. It currently takes 6 12volt 18 amp hour sealed batteries which are wired in two banks of three batteries in series to yield 36 volts each which are then wired in parallel. Wired as such, what is the amp hours of this configuration?

These things currently need replacing and I'm wondering if I couldn't replace these with three 12 volt car batteries wired in series? And if so, what would the difference in amp hours be? Automotive batteries don't show "amp hours" per se but I imagine the "reserve" would play into the longevity of a charge.