Rear frame rail fitment

[hemi31]

Does anyone know what the difference or differences in early(pre 67) vs post 67 rear frame rails. Looks like the rear frame rail caps fit both generations. I have a line on good rear frame rails locally for my duster but they are from a 66 barracuda, I need to know if I can make the work or if they are completely different?

 

[Syleng1]

I believe they are not long enough. 66 is shorter.

 

[Kern Dog]

My information is that all frame rails are physically similar, front and rear. The front rails are 1 3/4" further apart from 1967-76.
The rear rails from 63-67 will have a notch for the gas tank strap. 1968 and later cars used the fore/aft dual straps for the gas tank.