Reversing polarity often does not blow fuses...(sometimes it blows the main though)...rather it toasts control units like the ECUs, PS controllers, some AUX relays...circuit boards like what's in the dash pod..ect. Usually starting from the battery you will have your main system fuse, a 20 or 30 amp, then a distribution box with your smaller system fuses. If all that is OK, then you will need a wiring diagram to start the tracing process.