Sorry I never replied, I got it sorted out and set out for Bimini
and forgot about it.
It turns out that I was incorrectly assuming that the thread was damaged. What actually happened was : the original alternator
bracket used two bolts, and the threads for one was US and the other was metric. I did not realize this, and when I ordered the replacement part, I assumed the threads were the same as the original. In fact they were both US on the new one. So I was trying to screw the metric bolt into the US thread on the new part. I finally figured this out after some head
scratching, and a quick trip to Home Depot for the right bolt sorted it out.
Thanks for the tip though, I think I'll pick up a tap and die set when I can.