just keep it to a nice and safe 5-6 psi and you can use the stock injectors and get the supporting mods around it setup right and it will be a great power improvment over the stock
I am pretty sure luke was using stock injectors and was running his D at 11psi but i would just get a bigger fuel pump to be on the safe side.
I would use that bit of saved money to get a good quality high flow exhaust setup and no muck around with cats from other cars etc dont get the exhaust right and even if it has injectors etc it wont make as much power as having a good exhaust on it