The metal where the trunnion bearing races sit looks great, just a little dirty still. When I removed the old races they were still sitting in there nice and tight, no slop going on there!
Regarding the spring hole pin, I figured I could just weld it back up and redrill it. The U-bolts were still tight when I removed them, I'm guessing at some point they were loose which allowed the spring pin to move around too much?
It shouldn't be an issue getting out the old drain plug as I was still able to get a socket on it. Worse case I can weld a nut on the drain plug and remove it that way. Once I get the plug removed I'll run a dremel on the inside of the metal ring protector to clean things up a bit. I'll certainly consider swapping out the hex drain plug with an allen wrench style, seems like a no-brainer since it's close to the rocks. There's also a good sized dent in the diff, it should be easy enough to just pop out from the inside using a little heat and a BFH.