A-body door crash bar info. When started?

[Locomotion]

I'm pretty sure 1971 A-bodies did not have a crash bar in the doors (Duster/Demon). Did they start in 1972 ,1973 or 1974?

 

[2 Darts]

My Demon does not have crash bars in the doors. However, the doors came off different cars. (I know for a fact that the passenger door is a 72.) My 73 4-door does have bars in the doors.

 

[Locomotion]

Thanks. From some other sources, it seems that they may have started putting crash bars in Dusters/Dart Sports in 1974, possibly mid-year 1973.

I don't know if using 4 door examples would be helpful. They may have gotten safety stuff earlier because I believe they were a year ahead on the transition to the shock absorber bumper brackets.