Stalls after start

Any applicable trouble codes? Does your check engine light work? You can check some codes, yourself. Cycle the key, on--off, on--off, on, then the check engine lite starts flashing, you count the flashes to get the codes. Your looking for two digit codes. I did look up code for ais/automatic idle speed, code 25.
With idle issues, I would check that. I looked up your idle speed in specs manual, it said 750 rpm in neutral. You need a tachometer so you can watch the rpm's. Your dash may have a tachometer? That 750 rpm may be a little low, it depends. I also saw a minimum idle air procedure, It involves the ais fully closed and adjust the idle to proper rpm's with idle adjust screw.

I would clean the throttle body itself as a start. It doesn't take much crud in there to cause idle issues.
Next would be to test the idle speed actuator. It is controlled by the ECM to set base idle and adjust the idle based on engine load. If it fails or the wiring to it is corroded you get no idle control. They tend to fail internally, there is a gear and threaded shaft with a plunger that controls the idle position of the throttle plate, the gear fails and the computer cannot control the idle. (Part in picture)

You can replace just that part but I like to replace the entire unit as it makes it easier to calibrate.
This same part is used on a lot of GMs of the same era and the failure is the same. Engine starts but won't idle.
ACDELCO 19160423 is the complete unit. Make sure it comes with the plate as they revised the stud location and the new part may not be a bolt on.

To install the replacement you need a tachometer and the wrenches to fit the nut and the throttle stud (you reuse that part, it screws into the end of the new motor)

Pull the air cleaner off, remove the neg. Battery cable.
Disconnect the connector and remove and replace the ISC actuator.
Swap the bracket if needed.

Connect the battery back up. Start the truck and let it run 2-3 minutes so it warms up.
Shut it off and watch the ISC, it should retract all the way.
Now unplug it and the coolant temperature sender.
Connect the tach.
Start the engine and check the "idle" speed it should fall between 2500 and 2600rpm.
If it isn't correct turn the extension screw (piece you swapped from old unit) until it matches that rpm.
Shut off the engine, Reconnect the sensor and ISC connector.

During this process you can set codes. Either disconnect the battery or use a scan tool to erase them. (Battery is usually easier)