I was thinking that the 1989 E350 460 already had the ICM mounted on the radiator support.
I do not know of an adapter harness to do what you want to do.
Some have relocated it by making their own harness. I think over on the Bronco II forum there was talk of doing it.
The one on my 1994 F53 the ICM is located in front of the radiator and to the drivers side.