MegaSquirt (MS3) or Holley HP EFI

I have a Terminator X and I'm starting to sour on the whole Holley ecosystem. I would definitely encourage you to really drill down on what and how you want to set up your car before coming to a final decision. If you think you are going to want to run other brand modules over CAN communication, forget about Holley altogether. Also Holley does not support an 8x crank trigger, so you'll need to modify the flexplate or run another trigger wheel that they support somewhere else.