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Bus a/c units typically have two to three condenser fans and two to three evaporator fans across multiple evaporators along with a second battery to reduce surges caused by fan and compressor cycling. Draw on the alternator can be 30 to 50A at idle! Between lack of charging at lower RPM and heat production at higher RPM the alternator may have one helluva job maintaining a charge. If you're in an area that gets warm and your vehicle is expected to do a lot of idling or stop and go driving you should plan to use a more robust alternator than an "upgraded" 10SI or CS130 style unit. At a minimum I would ensure selection of a 12SI alternator such as Delco 321-594 with an "undersize" pulley for an older bracket system. If you can fit a CS144 alternator there are more options all the way up to aftermarket 200A versions although you should be sure to match output and armature RPM to your engine speed so there is sufficient charging at idle. If you have the room an AD244 alternator such as GM 10480390 might be more desirable due to larger case, larger cooling fan, and ample ventilation. With this much current being produced and especially with a smaller driven pulley you should also consider a serpentine belt system to be mandatory. Ultra-cool looking single V belt systems simply cannot transmit the necessary torque to the alternator pulley without putting excessive pressure on the alternator bearings.