everything's going smoothly so far. all i had to do was swap the hard drive for an older one.
for some reason it had a 500gb wd blue from 2016 in there that was probably way too new to work properly (old macs with sata controllers are incredibly picky about sata 1 implementation and a lot of modern drives just Don't Do It Correctly).
i pulled the drive and saw that it had... part of a zpool on it? so it def hadn't been used in this computer. anyway it was a mirror so i could still see all the files (some of wich had been created well into the 2020s) sorry to whoever those backups belonged to i guess.