72 Blazer on/off rd package?

[krc400]

Maybe this is a dumb question, but just what is the on-off rd package? Thought maybe it was the rims? Just curious if anyone knows. I put a new gas tank in the old gal and she fired up after sitting for over 3 years! Blew a lot of rust and a mouse nest out of the pipes too! Needs a little brake work but after that its on the road again. Can't believe someone let a truck like this sit outside and rot! At least the last 2 years were spent in a garage!