Chosen Solution

I’d like to replace the optical drive of my MacPro 2.1 with Blu-ray writer. How to choose the drive. Is there a list of compatibility or it doesn’t matter. Can I connect optical drive to HDDs 4th bay if not used instead to SATA connectors beneath the front fan assembly.

Here’s what you need:

LG Super-Multi Drive Mac Pro Kit 16X 5.25" Internal Blu-ray/DVD/CD WriterComplete Kit for 2006-2012 Mac Pro modelsIncludes Toast 17 Titanium + HD Plugin https://eshop.macsales.com/item/LG/WH16N

I don’t know of any internal SATA BluRay drives that will work in your older Mac Pro. The one I’ve installed is this one LG Super-Multi Drive from OWC in 2012 model. I think you’ll need to stick with an external drive like this one  OWC Mercury Pro