First of all, thank you very much for the props! I've put in a lot of work into improving MPGuino, and I'm glad to see that people are using the upgraded code.
1). Based on what I saw at RockAuto.com, I'd have to say that your fuel system is indeed a constant-pressure version. You'll need to compile in the returnless pressure option when you compile the MPGuino code, and set a fuel system pressure of 48 psi.
2). There is no list that I know of that has cars that have this constant-pressure regulator. It'd be good to compile one.
3). If the fuel pump does cycle on and off to keep pressure at 48 psi, then there will be times when fuel pressure will be above the pump's setpoint, and there will be times when the fuel pressure will be below the pump's setpoint. Will this cause fuel pressure to vary? Yes. Will it make a noticeable difference? Maybe. You'll have to experiment and let us know what you find.