The biggest thing with a crossflow 4/4 is to protect the feed from the starter relay/solenoid that runs across the car to the fuse box. Unfortunately I can't find my photos, but it is worth putting a 30 or 40 Amp fuse at the solenoid end - should stop any magic smoke getting out.
As for calculating fuse capacity for each circuit, there is plenty of info. on line. If your car is anything like my old '76 there are only 4 or 5 fuses in the car. A lot of circuits are not protected, for example, headlamp circuits.
