I suppose you mean the jack instructions in the first pic. Can't say for sure, I only got the truck in 1989, though I can't say why the original owner would change the decal.
Come to think of it, the jack I pulled from the truck seems to match the decal
I was informed it was the wrong jack. Hmm. Both replaced or factory?, hmm.
Seems the jack's bracket installs either way, my 72 is like yours. I found my 71 like what's pictured and it matches the assembly manual, pic. 5.
Cab wasn't replaced but interesting that decal and jack is for a GMC. Might the difference be my 71
SWB 2WD was ordered with leaf springs, which came stock on GMC? But then, why would the jack be different for leaf springs?
For what worth here's the jack I removed from the truck, which matches the decal instructions. Not saying it's original, but I learned long ago what must be doesn't always apply. Other than that, I can't find those instructions anywhere.