Getting ready to swap a 5.7 into my 73 Dart Swinger

Stuck, i need a new fuel regulator i think im seeing a ls1 regulator will get me 58psi. Now here is a question.. I have 03 injectors that are supposed to run on 48 psi +-2psi. The computer has been changed over to a 05 which says it requires 58psi +-2psi.. Right now my regulator is all over the place with psi and my gas tank was also super presurrized after trying to start the car.
Also someone mentioned keep an eye out for details about different tone rings on the 2 different years?
Currently its just cranking not starting everything has power and ground it is throwing 3 codes a believe for iac or too little air???... Pedal doesnt seem to move the throttle body but will it even move if the car isn't on? I read another forum saying only moves when car is on.
Otherthings im going to check for is
VATS- vehicle anti theft system i have heard both sides plenty that it does or doesnt have vats
Battery-stable 12v while cranking
And tps relearn
I have hp tuners but havent yet even figued out how to use it.. Learning as mush as i can