Rosie casually drops the term "Mickey Finn" to refer to a near-toxic combination of whiskey and sleeping medicine. According to the Wikipedia page for this term, Mr. Finn did indeed commit his drug-and-rob crimes about three years prior to the action in this film but also indicates that while the crime was mentioned in Chicago newspapers the term itself wasn't in popular usage as a stand-alone noun until several years later.
As the third of three riders are exiting(Jan-Michael Vincent)the train at race station(close to 12 minute mark)you can clearly see a crew member wearing t-shirt,sun-glasses and wrist watch looking perfectly mid-1970's.
When Sam Clayton takes the saddle off his horse at the end, it's clearly dry under the saddle, while the rest of the horse is wet and lathered. The lather and dampness is clearly fake sweat, as it would be soaked under he saddle also.