I would second Nelson's recommendation: the 37/44 tooth combination shown there yields a 1.2703:1 ratio: very close to the ideal 1.2700:1 ratio. according to Logan's web site, it's only 2/100s of 1% error. the 54/44 combo yields 1:2273:1.

Kudos to OlderDan for bringing this to the surface: an easy way for inch-based lathes to cut metric threads!