Give Nathan Dagley a call , I'm pretty sure that he can do it , it will oikely involve a gear change in the head of the lathe but it shoulden't be that big of a deal for most lathes if the gear is available.
I know that they make a Tap that converts the metric threads to american , so their should be a fix to single point the threads to american , I'm not sure how good of a job that will do but I've heard it can be done.
Best bet would be to just true the factroy threads.
I'm taked to Peter Lincon a good bit about the Howa actions and in his experiance which is ALOT , they require very little work to "true" them up. In all honesty they are a superior desgine to the Rem 700