I feel like I'm missing something. Isn't there some sort of top plate or something between top of spring and mount?
https://photos.app.goo.gl/q3pDm3WtjfXrmL3b8
He raises a good point. Short term memory issues, but i KNOW something must be wrong there lol. I believe you forgot to swap a piece from the old strut assembly to the new one here. Once the crusty old one is on there, you'll know if the top of that spring is correct or not.
I also couldn't find replacements for my spring seats. They don't make noise so add it to the "some day" list