Need help with frame identification.

[Richs'55]

I have a frame that came with my '55 body and cab. Replaced the frame with another C-10, but would like to identify the old frame.
4X4 and think it is around 1978 or so but don't know for sure.

I did find these numbers on the passenger side about under the cab area.

Can some one decode these for me.

First, on top of frame under cab.



This one on the outside of the frame under cab.