+2 on these last to posts!

It's not all that critical, and as ultraman says, the pitch is exactly the same.

A brief story here:
I recently put a 1972 Peugeot fork on a 1976 Motobecane, replacing the moto fork which had a freshly-broken dropout.
I first had to thread down and shorten the Peugeot fork for the smaller Motobecane frame, but didn't have a French die!
So I just used an English die on the Peugeot fork steerer, adding 1" of threads, then cut it shorter with a hacksaw.
I found an English-threaded top race for the headset since the French one wouldn't fit, even though the steerer was originally the smaller French diameter. Everything then torqued up fine.
Lastly, I had to remove some unwanted paint from the half-chromed Peugeot fork, then file down a Japanese 100mm stem to fit the French steerer.
Moral of the story? As long as the locknut is kept secure, it's really hard to mess up headset threads, unless a keyed lockwasher spins and tears away a row of threads.
BTW, I broke the dropout while trying to twist out a stuck stem, which I ended up having to saw off just to remove everything.