1970 Super Stock or Pro Stock Darts

Hi all, I am wondering about some pictures I have seen of 1970 Darts. They appear to have been running in Pro Stock. The cars are from Dick Landy, Melvin Yow and Larry Griffith. I know these were not factory produced race cars. I just figured they were 1968 Super Stockers the racers changed over to the 1970 body style or they just built them on their own.

Does anyone know anything about these cars?