I am putting in a Trans cooler as was recommend here (thank you.)  I am also working on the engine and front drive-line and other leaky things and have the fluids out and so cannot use the run the engine to see which hose heats up method to see which side to install the cooler lines on. Can anyone tell me whether it is drivers side or  passenger side that is the upstream side?
 I have to say that the more I work on this trucklet the more respect I get for Suzuki/Geo. No wires hang below the from rails, the gas and brake lines are tucked up inside the frame rails, the timing cover is gasketed against water and the crank speed sensor can be swapped in fifteen minutes with a 1-mm socket. This is going to be a fun off roader!

Late reply, but is this on your 96?  The 2-door should have the GM TH180 3-speed automatic, vs the 4-speed in the 4-doors.  The only information I can find lists the return line in the rear of the transmission, it doesn't list left or right side.