The output of your alternator is irrelevant to this issue. What matters is the connected load and unless you have a huge load of some sort, you want the breaker from the alternator to the battery to be sized small enough to protect the battery and the breaker from the battery to the interior controls of the car to match connected load. Things that effect connected load would be sound systems, amps, high power ignition systems. Caveat here, all this happens after the MAD wiring conversion!
Mine is basically stock so I opted for 40A from the alternator to the battery and 30A from the battery to the interior. Works well!