Snip
  If the thread actually *is* 10-30 UNS, count yourself lucky.


Exactly.  When I wanted to fix up an old lathe I bought years ago, I had to
special order British Whitworth bolts to replace some chewed out ones.  The
guy at the bolt place said to me- why not just run a tap through and covert
to standard?  I even special ordered some BSW Helicoil kits to repair some
stripped threads.
All that was expensive (compared to using what I had on hand), but I did it
anyways.

Because otherwise, it wouldn’t still all be “original equipment”, right?

  I have always tried to use original parts or at least replacement parts
that could pass as original.

But really, now that I am older and supposedly wiser, who the hell else is
ever going to really care?
Cheers
Claudio