Okay if the ecu plugged into your harness then it is a 90-91 ls ecu, if it was a 93 it would be obd1 and it would not have plugged in. Now about the resistor box you need to find out if the injectors are peak and hold or saturated.
Peak and hold means you need a resistor box, saturated you don't. To find out take a mutimeter and get a resistance reading across the terminals. If it is between two to three ohms then you have peak and hold injectors and need a resistor box. If the rsistance is much higher, 9 to 10 ohms I believe, then you have saturated injectors and you don't need a resistor box.
AS for thye distributor what are the colors of the plugs? If they are white then that is a 90-91 distributor and it is what you need. If the plugs are grey then it is obd1 and you can't use it.
Use the stock dx harness.