I had a very similar problem to this on an '86 I fixed up. The problem was, you'd have to do some wiggling of the shifter, and you could eventually get the shifter in park. But once you pulled it out of park, it was a real pain to get it back in. I was able to get a complete used shifter out of the local junkyard for $15-$20, so I tried that, and sure enough it worked great.
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