Since posting, I replaced my 100mm Suntour suspension fork with a 490mm carbon fiber fork. The new fork is just a little shorter than the Suntour was when fully extended. It doesn't affect my riding position noticeably. I'm really happy with the setup.

When looking at brake mounts, I found this helpful for explaining the standards: https://www.bikeman.com/bicycle-repa...4mm-post-mount

And I found this most helpful for adapters: Art's Cyclery Blog » Rubber Side Down | Disc Brake Adapters