Factory big block trucks?

[Barnfind46]

I have a quick question.My dad bought a 67' or 68' C-10 when I was a kid back in 1973.The truck was six or seven years old so I don't think it had been messed with much.It had a big block 396 with 400 auto.Did they put the 396 in trucks or was this a swap? I later learned to drive in it and started maintaining it. (changing alt,replacing rocker arms and stuff like that)It was the ever popular orange/red with white top CST. I bought a 68' C-20 in the same color 14 years ago that was a painted bumpers no trim truck.Every time I climb in it I am 16 years old again!