Originally Posted by
Recoil
429 fordman beat me to it. I currently have a 77 box in my 76, no problems.
That's because both the 1976 and 1977 use a Duraspark-II module. Blue Grommet.
The 1975 uses a Duraspark-I, Green Grommet.
The systems are not compatible with each other.
Why the Blue Grommet DS-II module didn't work, after he changed his wiring to the 1975. He now has to use the 1975 DS-I module.