It's usually the resistor that goes, though I'm not sure these cars have them. If it is the motor I would go and get a Made in USA/Canada one from the junkyard. Any new one you get is likely going to be Chinese. They're not that bad to change out once you've done it before (though I'm not sure of the Eldorado, just in general).
As a sidebar to this thread, I've ordered the engine tilt tool, and it should arrive tomorrow. In the meantime I've tested 5 blowers on the shelf in the car, all but two worked as designed. The two that failed actually ran, but vibrated so bad (cracked fans from being dropped) that they were rejected.
I took apart one of these to see if I could swap out the squirrel cage; looks like you can.
Another interesting discovery was the lack of the heavy 'weight' on the back of the motor on two of the good examples. One was an obvious replacement blower assy (white EASILY replaceable squirrel cage and three hole mtg.). What's the purpose of that heavy disc?