They are very nice figures sculpted by Mike Owen and still some of his best work IMHO: I always liked them, gave them their individual names and wrote the series of supporting articles that appeared in WI to accompany their release.
In short, they're dressed for their time period, 1820s-1840s. Some would take relatively little work, e.g. Jim Shaking Snow and a few of the others that don't appear here. With Jim Meredith for instance you could get away with a head swap or at least replace the hat. Others would require a lot more work, and in many cases it would be easier to start from scratch. By the time enough changes had been made to push them back a few generations, I fear a lot of the things that charmed you about them may well have been lost. For instance, although many Canadians in the backwoods may have been unshaven for periods of time, in an age when beards were about as "out" as they've ever been, such luxuriant tonsorial splendour as sported by many of the mountain men would have been rather more than unlikely.

I suppose it depends on how concerned you are about having them look right for the period.

If it were me and I liked them as much as we both do, I'd get some anyway (I have them all), paint them up as what they're meant to be, maybe run the odd skirmish between them or with same period Indians, or just keep them for their own sake

Then I'd go and buy some figures created for the F&IW

, let me think ... Canadian Militia from a company very dear to my own heart perhaps
Other manufacturers are available.
www.gallopingmajorwargames.com