You could use them using ehads or helmets from more era appropriate sets in lieu of the tricorns, but IMO
1) I doubt that a large portion of ECW horse was armed with carbines. These would likely have to be trimmed off.
2) The horse furniture looks a little too modern and military for the ECW.
Still when you don't have what you need this may be your next best option. I'm hoping ACTA will downsize their 1/32 ECW horse.
remember that the Reitars have turn backs, while most ECW cavalry would have had buff coats see: http://www.metmuseum.org/toah/images/h2/h2_15.113.1-5,29.158.885.jpg
So, if you make some buff coat out of model putty, and put some helmets on the bodies, you will have some ECW looking cavalry. (apart form the horse furniture and carbine's points Bill mentioned)