https://archive.org/details/ponychan_archive_ponybro
Sorry for dragging my feet on sharing my ponychan.net stuff. My internet upload speed is garbage, it's taken a while to get all the images uploaded. The .zip for /chat/ is over 6 GB and the upload is always interrupted at some point. Also /fan/ apparently failed too and I didn't notice until now, but it's only 300 MB so it should finish reuploading soon.

I've also been given a dump of the original 8chan boards /pone/ and /mlp/, by the creator of Hayden. He's started a public archive at https://ultra.gondola.pics/ of 4chan and he plans to add every dumped 8chan board to it. He isn't going to host images but said he'll figure out how to get the ones for the pony boards sometime.
https://thereisnosanity.com/mlp.json -- 141 posts
https://thereisnosanity.com/pone.json -- ~31,000 posts