Ford Repair: computer, ford f250, turbo diesel

Question
where is the control computer located on my 1990 ford f250 7.3 non turbo diesel,and where can i get the best deal on a new one.the e4od tranny has been overhauled and sometimes doesn't go into 3rd from 2nd without reving engine

Answer
your diesel has no computer control.  1990 7.3 engines still used the mechanical injection system, electronic engines did not come into production untill the late 90's.  Your transmission problem is not electrical either.  your transmission is acting typical of rebuilt transmissions, shifts are no longer as smooth and they act clunky.  im not familar with a e4od trans but i think 1990's came with c-6 transmissions.