If things are OK now I would suggest leaving it as is & concentrate on the issues that need to be dealt with. If you pull/clean the bulkhead it will take care of most any potential electrical issues & never use the alt to charge a depleted battery (use a regular battery charger). Otherwise as said the 78 amper is the most powerful stock one except for the big 100 amp beast with the fan blades behind the pulley & it has special bracketry & is heavy but is a good piece. the 78 amper has a thin stator so a slight fore/aft mounting adjustment is needed (washers/spacers)