It will work with no adapters, etc., needed.
I've done it. Having PATA available in the DVD bay saved me on an occasion or two when I had to retrieve something from an old drive. About the only issue that might come up is the configuration pins, though I left those alone and didn't experience any problems.
It was fun seeing an old 20 GB drive from (I think) an upgraded Power Mac 7500 show up on my desktop! It was like time travel.
(I do agree, though, that an old drive like that is not optimum for use as a backup, at least due to being power hungry and adding noise.)