I've done what you describe, matching up a Wargames Foundry Indian Mountain Artillery crewman's body with a Woodbine head, though it was one of the "wounded" heads with a bandage. I've also matched up an Empress Miniatures Zulu War head in a Glengarry with a Woodbine body. IMHO both resulted in nice, smooth conversions. I've also done wider-ranging, full unit conversions of various Second Afghan War Indian Army and British units, but never utilizing the Woodbine heads.
To be honest, if I'd been aware of the "Hindi" head sprues back when I had to convert the turbans on 20+ Perry Sudan "Bengal/Bombay Infantry", rather than painstakingly sanding and etching and gluing bits and pieces onto each individual head, I probably would have just lopped them all off and replaced them, as the Woodbine "Hindi" heads look eminently appropriate for c.1880 Indian infantry.
Unfortunately, due to the way these particular pics were originally saved/uploaded, I can't repost them here, but here's a link to visit the appropriate page of my blog, where the figure in question starts out as an artilleryman kneeling w/a ramrod in his right hand, which is removed and replaced by a canteen (courtesy of the Empress Zulu War accessories pack)
link
As far as using Woodbine heads on Old Glory bodies
I think that would be a hit-or-miss proposition. In my experience Old Glory colonials are sometimes a bit smaller than their Foundry colleagues, but other times they are virtually identical in scale, so you never know.
Good luck, and hope you post pics of any such conversions you do!