As I mentioned in step 9, I was punished by the lack of threads in my new window regulator

So I broke out my tap and die set, and checked the bolt thread pitch, which was metric M6 x 1.0

I didn't notice until I'd already slipped my new part into the door... I actually pulled it back out of the door to tap the four holes

If your part also has a lack of threads in the holes, be sure to check it before you've put the clip through the pin, and reinstalled the track bolts etc