Best approach will be to add up all proposed loads yourself and divide into two categories. More on that later.
Worst case scenario would be to add up amp ratings of each fuse and circuit breaker in use at one time.
More typical scenarios can be constructed using the actual ratings of your components, and if not known, estimates from general sources; Here's two:
* Page 8, even though its for heavy trucks in ACDelco Starter and Alternators (pdf)
* http://what-when-how.com/automobile/vehicle-electrical-loads-automobile/

It will be best to identify and seperate the two situations that will occur:
a. Power draws when the is alternator is supplying power.
b. Power draws when battery alone is supplying power.
Diagrams from NachoRt here show why.

Because the modifications proposed include electric fuel pumps and efi it would be prudent to spend time engineering the system because (b) Loads on battery power alone, will be very different than the original system was designed for.

Explanation: Power for the efi and electric pumps must be supplied during starting. They will be drawing off of battery alone. It will be critical for them to get enough power and the battery drain will be higher.
Definately look at relays and wiring to insure minimal losses and keeping current through the charge, start and ignition circuits within their capacity.

Alternators
* Keep in mind that during lower voltage situations (battery only), current to the equipment will increase. Almost as bad will be when alternator can not keep up to demands. That's why its important to size the power output vs load at idle.
* Since alternator power out varies with voltage and rpm, manufacturer's sometimes play games with the ratings.
* The single wire is a self exciting circuit. If you prefer internal regulation, it would be better to use a voltage reference located closer to loads and distribution.
More on this here.

my is that is all very doable but worth the time and effort to design it right from the beginning.