How old were the actors in Heaven's Gate (1980)?

Harvard graduate James Averill serves as the sheriff of prosperous Jackson County, Wyoming, standing at the center of a conflict between impoverished immigrants and affluent cattle farmers. Politically connected ranchers enlist mercenary Nathan Champion—who is also vying for the affections of local madam Ella Watson—to combat the immigrant uprising. As tensions escalate, both Averill and Champion start to question their decisions.