The current rating of the alternator relates to the maximum safe output current. The alternator will only supply the current that the electrical system requires so the bigger alternator alone should not cause problems. If you have added extra electrical equipment then the extra output may be useful but may cause problems with existing wiring which may overheat and eventually melt. The fuses are fitted to protect the cable and should not blow unless there is a fault or someone has fitted extra equipment to an existing circuit.