the 50 at the end doesn't reall matter that' just the warranty period of the battery. for example yours the 24f-50 would be a 50 month battery, 24f-60 would be a 60 month battery and so on. the important numbers are the first ones 24f 24 means it is a group 24 battery and the f signifies it has ford style post arrangement.
to answer your question simply yes a 24f battery is the right battery for a small block 69 stang.
some of the big block cars used the 27f battery and i believe the 27f could be ordered for heavy duty use or cold climate or whatever you wanted it for basically it was an option