I think there is a tag on the back of the tcase with it's info. I don't remember for sure. Looking at your picks again, I think the crack is next to the tcase shift linkage. I Don't weld aluminum either. I'll look at my transmission tonight and let you know if I'm interested. It's a pretty good hike to you but now undoable.
I looked last night and I did not see a tag on the t-case, it was getting dark but I did not see anything obvious. I took a few more picture of the crack at the t-case shifter mount. Would you like me to text you the pictures?