So I swapped out my steering column in the 91 GTA since it was damaged when I bought it. The new column comes from a 91 GTA as well - both are 5 speeds so everything swapped no problem. Checking the resistance on the two keys showed that they were different so of course the VATS won't allow the car to start.
My questions is - can I just go to the dealer and get a key made up with the correct chip in it? Would that allow the VATS to work again?

I realize from searching this site that I could just solder in the correct resistor inline but I prefer to keep the wiring stock.
Another fix is to swap key cylinders but I put my manual in a safe place and haven't found it yet so I don't want to start digging into the air bag wheel without it.

 

Yes , I have done this same thing to a column swap that I did not want to dig into the nice low mileage column I got to change the lock cylinder . You will need them to get a key blank matching your original key (this will or course have the right resistor in it) and they will need to cut the blank to match your new column's key . That will produce a key that both satisfies VATS , and allows the lock to turn .

 

You really shouldn't need to solder the resistor in to bypass VATS. Just disconnect the VATS plug under the column and bend the pins on the resistor to fit in the plug snugly. Then fold the resistor over the top of the plug and tape it good so it doesn't move.

 

I tried my new key today. It didn't work at first, After a bunch of tries, it fired up and ran with no issues. Next time I went to start it - it didn't work. I realized I had used the old key so tried with the new - no luck. There is lots of power - just nothing happens at the starter motor.
Did I inadvertently set off the VATS with the old key. Is there a reset procedure once VATS is triggered?

 

Just figured it out - it is probably in Tamper mode and needs time to reset. I'll try again in the morning.

 

Just confirming that Tamper mode was the culprit. I had to wait a lot longer than the 4 minutes though.
The new key only cost $36 from GM and was well worth it.