Is it a cube bus or a passenger bus? Actually, according to my application guide, you're vehicle either has dual 110 amp 6G Series alternators, a single 130 amp 3G series alternator, or a single 215 amp Mitsubishi alternator in the ambulance prep. Could you let me know which alternator it looks like you have? There are many upgrade paths, but you will definitely need a Quicktifier Remote Rectifier and a QuikCool System to help keep your charging system cool when stopped and idling, when the alternator has no airflow. Let me know some more specifics on your charging system and we can go from there. You can find the Quicktifier and Quikcool at
www.alternatorparts.com