have you checked george's site, utterpower.com?
i am sure that is where i saw a link to a guy who has a site detailing a regulator for the ST head.
if not on his site, then it is on his CD listerlongevity, which i might add is well worth the cost, it not only has info on the listers, but also the chinese diesels, and the ST heads.
come to think of it, that is probably where i saw the schematic for the ST regulator.
anyhow check out george's site, and email him for details.
bob g