Here is what Interstate battery says about RC vs AH conversion. This number does not agree with numbers listed here. "To calculate the estimamated ah rating for your automotive or deep cycle battery, take the Reserve Capacity Rating and multiply it by .6 to get an approximate AH rating.
Amp-Hour: The unit of measure for a battery's electrical storage capacity, obtained by multiplying the current in amps by the time in hours of discharge. Example: A battery delivering 10 amps for 20 hours = 10 amps x 20 hours = 200 AH"
I agree with Mex on this subject