Yo adjsnow,
AOD & C6 do not need an ECM to operate & both are bank fire, BUT Firing orders are different.
The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8
5.8L is 1-3-7-2-6-5-4-8
Some have claimed that it wont run right, and that is confirmed by a former Ford EEC IV & Ford Fuel Injection expert that the ECM needs to be from same engine type for your 90.
Others claim it will work, but never bothered to state that THEY did the change.