The dragoons have the Napoleonic long tail coat and open waist coat, so I cut away the tails and used some green stuff to make the more baggy trousers reminiscent of the 1870 era dragoons and a 'skirt' of green stuff to extend the coat and a thin 'belt'. I cut of the plume and smoothed the cut with some 'wet and dry' sandpaper. Then it was a paint job.
I have also tried creating a dismounted French Chasseur a'Afrique. Twisting the head off worked and I removed one of the belt straps. It sort of worked, overdid the green stuff on the back.
Update: Thanks to wellington Man and others for pointing out what I thought were early Minifgs are actually Hinton Hunts dragoons.