I know you need 7 guys on the LOS. But do 5 of them have to have ineligible numbers (50-79)?

Is there a rule that states you must have a specific number of players on the field with ineligible numbers?

Thanks in advance.

Numbering requirements only apply to those players that are eligible(1-49 & 80-99).
A player is eligible by both position AND number. If the player is not eligible by BOTH of these, then he becomes ineligible.
Therefore an ineligible player could wear any number, but an eligible player can only wear the numbers shown above.

Yes.

NFHS Rule 7-2-5
"Player numbering requirements include:
a. At the snap at least seven A players, five of whom must be numbered 50-79, shall be on their line of scrimmage."

I don't have a rule book, but continue to read, something about an exception, except in a scrimmage kick formation. So, if a team is in a scrimmage kick formation the numbering requirements are gone.

The numbering requirement is gone but positioning requirements remain for players to be eligible to go downfield and catch a forward pass.

Correct on all of the above, and don't let the coach tell you "but # 45 has been our tackle all year and no other crew has called that. They all said it was ok." We heard that one a few game ago. I just said, "well coach, they should not have let you, and we will not let you so you better get a different number on him." Fun way to start the game!