I'm right there with ya. The turbo I just put on had stripped threads in it and I didn't even notice until we we're putting it on. I have a bolt in the back and a stud with a nut on the bottom in the front right now.
You can get studs from the autoparts store that fit also. You can use GM header studs that are m-8 and m-10's (i'll look for sure and try to get pics) if you have stripped them pretty good and need to tap them out to the next larger size. The studs will screw all the way down in and lock in just like UP studs. If this is done with a little threadlock the first time the TMIC comes off there will be no need for the bottom nuts. Slotting the hole in the TMIC will help save threads also.
Oh and I've had mine on and off of the stock turbo a hundred times and it used to just drop right in. After the turbo swap; not so much. I had to get a leg up and lean on it a little to get it bolted up the first time. I'll go back and mess with it, but I know I'll be tapping new bolt holes and stuff, so I'm in no hurry as long as it's holding for the moment