The 85-88 2.5 (Edited to add manual transmission
) equipped cars all came with an Isuzu transmission. You can tell if a 5 speed has been swapped out by looking at the shifter cables. A Getrag 5 speed will have one cable going downward at the transmission and one coming upward. An Isuzu 5 speed will have both cables running parallel to one another and approaching the transmission in a downward direction. The 4-speeds are similar, but of course, you can't find 5th gear with those.
[This message has been edited by fierofool (edited 09-15-2013).]