Upgrade engine to an HO

I am changing the factory heads to the e7's and the factory cam to the HO cam. I know this will change my firing order. I also want to add a mass air to the system since mine is speed density. If i change my computer to an 89 mustang. Is there other wiring that my need changed to make it work right? I know the engines are similar minus a few different parts. Can you advise? maybe send me some diagrams for the mustang. I do have a factory town car manual but wiring is vague. Thanks!