You only need the one from the drivers side near the alternator. It plugs into the loom that goes down to the alternator. Yes it has fuses in it that you dont need like lights etc.

A main power feed goes into this fuse box to run the car.

I have removed the fusable links and used a 100amp circuit breaker instead on the feed to this fuse box. But you could re-use the fusable links. Some cars have a 100amp main fuse at the battery terminal. Which is a option if the battery is up front.

hey guys i was looking for the main fuse box with fuses, fuseable link n relays in it the 1 near the battery on a 180sx or silvia. i was speaking to the wrekers n he said i need all 3 fuse boxes to make it work. i dont think so cause the other 2 just run lights n #### like that!! anyone got ideas for me in the wiring ca18det up?? please help.