Fortunately, you can still turn the key (it is an absolute nightmare to remove these if the key gets stuck). You need to turn the key to the second click/ON position in order to remove the electrical pin plug from the rear of the ignition housing. With the key in the ON position you can stick a paperclip or hairpin or whatever into the small notch on the front of the tumbler to depress the locking pin which will allow you to unscrew the black cap. Then it's a relatively easy matter to extract the tumbler, unplug the vacuum lines, and remove the housing.

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