As far as electricians are concerned, you only need to have the MCA and MOCP. These numbers are required to be on the unit label. The MCA gives you info needed to size the wire for the unit. The MCOP tells you fuse or breaker size. In your case, MCA 37a tells you that you must have a wire with 37a as the minimum ampacity. Anything larger is fine but unnecessary. Best choice is 8 AWG for this application. If the MCOP says 50amp, you can use either 50amp breaker or fuses. If the unit says MCOP 50 amp fuse, then you can only use fuses. This is more common for mini split type systems than traditional AC units. Most traditional AC units also say type HACR breakers, which most breakers are. The info for these units is already factored with proper adjustments. Just read the labels and it will tell all.