Mounting location??? If I had to do mine over, I'd mount all fuses and relays high on the engine side of the firewall. Makes it a lot easier than trying to get my fat, 75 year old, 6'5" body under the dash.
Main breaker/mega fuse??? I use a 30 or 50 amp (depending on total system power draw), self resetting circuit breaker connected to the battery cable at the starter solenoid/stomp switch before any other electrical devices/wiring gets power. Remember, fuses don't protect the devices, they protect the wiring. Under $10. Looks like this:
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
