Well, I can't say what happened to Jim Burk, but here is the list of joint ventures with John Wayne and Jim Burk -
The Shootist (1976) (stunt double) (uncredited) (stunts) (uncredited)
The Train Robbers (1973) (stunts) (uncredited)
The Cowboys (1972) (stunts) (uncredited)
Big Jake (1971) (stunts) (uncredited)
Chisum (1970) (stunts) (uncredited)
The Undefeated (1969) (stunts) (uncredited)
True Grit (1969) (stunts) (uncredited)
Hellfighters (1968) (stunts) (uncredited)
The Green Berets (1968) (stunts) (uncredited)
The War Wagon (1967) (stunts) (uncredited)
McLintock! (1963) (stunts) (uncredited)
The Comancheros (1961) (stunts) (uncredited)
The Alamo (1960) (stunts) (uncredited)
The Horse Soldiers (1959) (stunts) (uncredited)
His most recent work, at least according to IMDb, was a movie in 1992, Hero.
FWIW,
Chester 
