Edelbrock Pro Flow 2 EFI system for Dodge 360
Short version - they're repackaged 5.0 Mustang computers, apparently with a slightly modified tune. It's possible to have a Mustang still run with a lot of modifications and a stock computer, but there's a reason there are so many hacks out there for Mustang ECUs too: Modify a Mustang enough, and the stock calibration won't give you the best power or drivability compared to what you can get with tinkering with the fuel and spark maps.