battery replacement

Hi Has anybody got any experience of changing the battery in the R129 SL 280, very large oblong type battery which holds its charge but for precaution Im topping her up via trickle charge (CTEX MXS) every 2 weeks which works fine. Im having the intermittent fault in starting the old girl where...

The original Mercedes battery is just coming to the end of its working life and I would appreciate recommendations as to a quality replacement. There appears to be a whole range of units with different guarantee periods, AH ratings and Cold cranking ratings. Which is the most important factor(s)...