i'm kind of resurrecting an old one, but I found this thread to be pretty helpful as I had to fix a stripped shaft drain too.
I got one (actually 2 since i didn't understand how they worked) of the Dorman self-tapping oversize drain plugs. it mostly went alright, but i bent a part of the final drive (crap!). i did exactly what I was afraid of doing. the length of the oversize plug hit the FD and pushed it in. you can see it in the pictures. luckily it is not a problem any time soon. on the plus side I think it is sealing pretty good though.
in the pics, the large plug is a 14x1.5 which i bought first because i didn't understand that the oversize was built in. I thought I had to buy a larger size plug. the little one is an oversize 12x1.75 (which is not the correct plug of 12x1.5, but i figured it would work) that I used to tap the hole (i had to keep shortening the plug) and then cut down to the correct length.
thanks for the help all!