If I was doing a street car with a engine management computer and other non race car components I would segregate the standard circuits like the lights, horn, dash power from the computer systems. Then run a third power block for the pumps, AC coil and ignition starter coil.
Run a separate power cable to the ignition box from the main 12+ point at the master breaker output.
So now you have three separate power cables (the forth being the ignition power) running from the battery thru their circuit independent protection (I like circuit breakers instead of fuses).
Why? A car battery provides a huge amount of surge protection. The inductive components like the starter coil, starter motor, AC coil, and pump motors can induce voltage spikes in their wiring circuits. Running separate power feeds (and keeping the wires apart) will eliminate this to a very large degree.
This would look something like this: One big cable running from the battery + to the hot side of the Master breaker. Then from the output side, three separate smaller cables running to each of the common + for the circuits breakers or the + of the fuse blocks. Then each fuse block would feed their responsibility's.
The alternator is treated like a second battery. It's output is tied into the + side of the master breaker (same electrical point as the + side of the battery). This configuration will cut ALL voltage sources from the rest of the system.
The above is the basic main power system for just about any car you could build.