Introduction
I finally found an OEM optical drive for my HP DL360P G8 that fit in the front slot. It always had the cover for it, but I would rather have a usable drive in there.
Installation
Installing it was pretty straightforward. You have to attach the SATA cable (I ordered one separately, also from ebay) and feed it through the front. The cable I ordered wasn't long enough to fit the connector nicely (even though it was the official part number for the DL360P optical drive), so I added a SATA extender.
The server also still had a plastic cover that was blocking airflow to the power supplies, that I think the original owner just never bothered to remove
Here it's installed, and with a Windows 7 OEM DVD that I ripped to use for a proxmox VM: