I still have a working 6P that's stock. Is there something specific I should do to run it?

I got the Universal installer to work.Had to flash the userdata.img file. I figured since I was coming from a custom ROM i might have too because i had to do it before when flashing to a Pixel Rom. I grabbed that image from the first availible stock ROM 6.0. If you get stuck flashing back to stock with the boot.img, see this thread. https://www.reddit.com/r/essential/comments/ihhedy/psa_solution_fastboot_error_couldnt_parse/
Hope this helps someone.

Yep if someone could please upload the files somewhere that would be seriously helpful. I keep getting stuck where it reboots into recovery. It doesnt install and doesnt go any farther.