as far as legalities go, 383hatch is a better person to answer than me.
personally, i would hook up the evaporative loss and cats.
a LOT of nasties come out the tailpipe with unleaded fuel and its nice to know that a lot of them get filtered via your cats, especially if you spend more than a few minutes in a shed with the engine running.
and with the constant flow of fuel through a fuel pump, up to the rails and back again, the fuel gets heated up a fair bit. on a hot day you really want evaporative loss to be functioning so you dont start venting fumes out of your fuel filler cap, or worse, expanding your tank. your ute should already have a carbon can on it, but grab one off whatever holden you took the engine from and use the hoses you already have hooked up to the OEM points on the engine.