Glad to see this project going forward! The wagon is really cool. Love it!
I want to add some things to the good advice which has already been given.
I'm speaking from experience here, having built about 6 custom turbo systems and converting several cars from carb to EFI.
To further explain the fuel system demands, I want to remember a couple things about a carburetor. It has a fuel bowl that stores a small volume of fuel. The bowl has an air vent at the top. The float valve allows fuel into the bowl to maintain the level. Even if the fuel supply to the carburetor is briefly interrupted, the fuel in the bowl will allow the engine to "ride through" the interruption. Also, if the fuel entering the carburetor has air bubbles entrained in it, the air will escape at the top of the bowl, without affecting the engine.
For the carburetor engine, the fuel sender in the gas tank has a simple tube assembly that goes towards the bottom of the tank. Some air bubbles and brief interruptions are tolerable.
For a fuel injected engine, things are different. The fuel injection system does not store any fuel. The pump must deliver the fuel
in real time as the engine needs it. Also, the fuel pressure is absolutely critical. All the calculations depend on the fuel injectors having a constant and correct pressure differential from the fuel supply to the intake ports. The pump must deliver a constant, uninterrupted flow of fuel. The fuel leaving the pump has two paths. One is through the injectors and into the engine. The second path is through the regulator and back to the tank. When the injectors open and send fuel to the engine, the fuel flow is divided between the regulator and the injectors. The regulator requires a constant flow of fuel for its working fluid, and it will not regulate pressure if the fuel flow is too small, or if there are air bubbles going through the regulator.
So, in summary - the fuel injection pump must always supply a constant, uninterrupted flow of fuel, without air bubbles. The regulator must always accurately regulate this fuel pressure, in real time, as the engine demands change. The pump must be able to work against the maximum pressure required of the system, while still supplying more than the engine actually needs to burn.
So for the EFI engine, the fuel supply has a much more stringent requirement.
For cars that had a factory EFI engine, the tank has baffles and a sump in it, to provide the pump with a stable supply of fuel. I was lucky with my FWD A-body conversions, that they had a tank which was compatible with the in-tank pumps.
On my 72 Nova, it was different. The early cars had a smaller sender cap, where the pump would not fit inside the tank opening. You may find yours is the same way.
I used a small, external fuel accumulator. This is a solution which will allow you to make no modifications to your existing fuel tank, and retain a completely stock fuel tank so that replacements will be readily available if something happens. The accumulator is simply a small cylinder with 4 fuel line connections on it. There is one fuel lift pump (carburetor style pump - low pressure) which keeps the accumulator full. The fuel enters one of the side ports. The top-most port goes back to the fuel tank. Any air bubbles will return to the tank this way, in the event there is an interruption of the fuel pickup tube. The bottom port is the supply to the high pressure EFI pump, and the other side port is the return from the engine.
As for the pressure, it's pretty easy to figure out. The fuel pressure regulator has a base pressure which (if I remember) is 43 PSI for the Bosch 0 280 160 237 regulator. The design of the regulator senses boost pressure and adds this on top of the base pressure. So, if you are running 20 PSI boost, you would be making 63 PSI fuel pressure under those conditions. Therefore, the pump will be called upon to provide more flow than the engine needs (at maximum HP), while working against a 63 PSI pressure - plus the pressure drop and restrictions of the fuel filter and lines. That's a tall order for many pumps, honestly.
The LC2 engine you have is a mostly "self contained" system. Once you provide it with a solid foundation of a stable fuel system and solid electrical system - it will reward you well!
I hope this helps add to what the others have said and that I explained it clearly.
Sincerely,
David