If you are running, you can put whoever you want on the line, 50-79 wise, or fill the entire line with them. You can put 10 men on the line and run student body left/right the entire game.
If a team correctly runs a swinging gate play, you will see probably at least 9 on the line (including the snapper) and probably at least 6 of them will be 50-79 blockers.
I know....
I was giving an example.