Ok...so this is a HEAVILY overdue update.
Because of my wife and I being in a Bankruptcy and losing my job and having to convert our case and winter, Hotdog had been sitting idly by while our case gets discharged. There was a real possibility that I was going to lose my truck.
Anywho...on to the update
I ordered the trans-dapt O-ring, and the WIX number previously mentioned. Both rings failed to FULLY seal the leak as they were both square-cut rings. I had to resort to using silicone to fix the leak. This too, failed. Partly because I'm sure I didn't let it cure completely.
In the end, I pulled the plate again and cleaned it completely off and made sure there was NOTHING left at all. I ended up finding a 90 x 4 mm round metric o-ring from my local hardware store. It had to stretch a tad to get onto the plate ridge, but it stayed in place without requiring any kind of silicone.
As of today, hotdog is back up and running. I'll be driving him to my new job tomorrow.
Thanks for all your help guys!