HDD upgrade to 250GB successful!
I found a seller on ebay selling xbox parts, and they had a replacement 40 pin cable from a doaner system for 10 bucks shipped. Went with the easy route for now. I also wanted to test my temporarily gimped DVD drive pins

with a stock cable. Fortunately I didn't damage it

. Any non-Thompson drive needs to be preserved lol.
Do you have the HDD, PATA to SATA adapter, and 80 pin cable you bought (links, models, etc) that all jived well together in your build? I'll archive them.
In time, I'll likely upgrade to a 1TB (maybe 2?) SATA drive and the 80 pin cable. I went the lazy route for now. That said lol...
I did run into some hiccups

. A few tips to any one upgrading:
- Use a first party controller
- Put secondary drive or PATA adapter jumper in Slave mode (cable select didn't work for me)
- If using Chimp, DL the latest and greatest build from JRocky5s GitHub
- If you have older version of Chimp laying around, avoid it and delete the linux config file. Do not place in E: root like we used to do. It was causing conflicts for me.
- Use composite AV cables on a set that accepts 480i
After troubleshooting all that for a bit, I then had to DL & FTP over the XBPartition 1.3 app. This allowed me to format my F drive to "see" all available space. So now my F drive has ~230GB of disk space
Overall, very happy for now with the project outcome

. Ripping a few key titles from physical disc via DVD2XBOX as typing this. Will um... go find, a few others that are pricey online to FTP over.
Also, I've been happy with this HDMI adapter I bought as a quick fix. Reddit community had it essentially labeled as the best output for the tier of spend at $40. I remember Kaico had some OSSC drama couple years back, but overall like this product.
Kaico Original Xbox2HDMI