Prop the chokes open with a screwdriver holding the butterflys open. Start it up and see if it runs and how long. If it continues to run but picks up rpm then it is a choke closing down too fast.

Then the only question would be which one.

You could also have the floats set wrong. If you are sucking all the gas out of the bowls faster than they car refill then the floats are set too low.

I can't remember if this car has an early version of electronic ignition or not. If it does then pull the connection plugs at the ignition box, which should be behind the left headlight on the inner fender, and clean them with some silver polish. They may be tarnished to the point of them causing resistance.