87 GT should be a Getrag...but it doesn't really matter since the shifter is the same.
I don't have a Getrag here to reference....but it should leave the select cable (side to side movement) in the middle, and the shift cable (forward/back movement) with the cable pushing on the transmission side. So....center both....then where the shift cable attaches, move it away from the cable mount.
Edit to add....in case you are confusing the two cables....when both are centered, the select cable bracket will move, but spring back....the shift cable bracket will notch into gear when it is moved.
[This message has been edited by CowsPatoot (edited 08-11-2013).]