I have a book called "How to ski Mammoth" (Clyde Hiatt & Bank Wright 1975). It lists the major chutes and bowls, and thier pitches.
Phillipe's Max 50 Min 40 - of course the narrowness, concave shape and often rock hop exit make it pretty spicey
Paranoid 1,2,3 40/35
Wipe Out 1 40/35
Wipe Out 2 47/35
Drop Out 1 40/35
Drop Out 2 44/35 - I think this is really what we call Drop 3 now, as what we call Drop 2 now may not have been skied much back then due to its rocky throat
Cornice Bowl 40/30 - maybe back in the day, but not now, due to corperate grooming
Huevos Grande 52/45 - The top of Heuvos has not filled in since the new Gondola was installed. Of course, we have not had a great winter since then, but some people think the expanded building changed the wind loading. I hope it's not true, Huevos is a beautiful run that is very sustained.
Of course, the book does not list the really steep stuff (nor does the map) like Top Of the World, with scary lines such as Balls, Werner's, Junior's, Diving Board, Etc... Kiwi Flat (often called Star Chute) is also really sick. McConkey skied it twice to win the Gravity Games. During that comp, Guerlain Chiq-a-something skied a very ballsey and perhaps origional line, now called "French Face" that is very wild. There is also very serious terrain in the Dragon's Area. Check out the Head Chutes, or Old Faithfull. Yea, Mammoth got steeps.