I also purchased a mini starter from one of the TB vendors. So far it has started the car, but I haven't used it much. It is made in China, and the build quality is mediocre at best. It looks ok, but I can tell you that some of the gears inside are made of plastic. Maybe that is ok too, but the insides didn't look very stout to be cranking a motor (yes, I had to take a look inside before I installed it). The gear that engages the ring gear looked a bit rough and somewhat crude. So it does work but wasn't too impressive.
Also, the description claimed that no shims were necessary, but when I installed mine the starter gear and ring gear were barely meshed. I filed a fair amount off the starter housing to get the gears to mesh more. If you get one it may be a good idea to check the gear mesh even if they say it isn't necessary.
I'm considering getting an actual GM LT1 starter in the hope that the build quality is better.