You have to use something to hold the harmonic dampener up and in place to basically take the weight off of the taper cotter. Then with a really small punch and my hammer, I came at it from the top and hit different angles, all around to try and loosen it. I ended up pushing one of the corners in from one side and then hit it from the side, until it was loose enough for me to pull it out. After removing both pieces, I gave a few love taps with a rubber mallet on the back of the dampener to push it forward and pulled it out.
I have made a video on my YouTube channel if it helps. I had to remove the harmonic dampener so I can fit the Miata tail housing on the FCS5 transmission.
https:/youtube.com/@shifthappens1992?si=SyZn8XFxhwRNPTHA