Well Mac,
The golf cart batteries are the hot set up... They are designed to survive that sort of abuse. They are typically in the range of 220+/- ampere hour and can be depleted to 50% without damage. Lifeline AGM say that they can do this 80 cycles with no loss of capacity.
What you are trying to figure out is the rating given because car battery manufactures did not want to be held to a 20 hour rate for Ampere-Hour capacity. What reserve means (kind of) is "How long can I leave the headlights (~25amp) and still start an engine" that doesn't need a lot of cranking (because it won't be there). That measure goes from 12.8V starting at 25amps until the terminal gets to 10.5V (iirc). At 10.5 most Lead Acid batteries have been harmed. You get to do this about three times before that jar is toast.
Go with the golf cart pair in series.
Matt
