ECU question

[blown motor]

My old truck has stock mopar electrical with a five pin ECU. I had another one here that I swapped on just to see if it was still good, which it is. But it's a four pin. The truck runs fine with it. What's the difference and will using the four pin hurt anything?

[Bullitt-]

Later models changed to 4-pin eliminating the need for a dual ballast resistor, has the voltage controlled internally.  4-pin can replace a 5-pin but not vice versa.


https://moparconnectionmagazine.com/gallery-mancini-racing-reintroduces-the-orange-box-videos/