My cousin had one of those in a Buick Skylark GS 455. Dang thing whined like a wife on a small shoe budget.
It's toughness is legendary, though. However, the Ford Toploader has the most rigid case design, which is why Jericho racing transmissions are taken from that design. A big-block Toploader is probably every bit as tough as a Rockcrusher.
The best part about those transmissions is the fact that you'd have to do something spectacularly stupid to really hurt either of them. Modern aluminum-case manuals abound, but I wince at the thought of power-shifting them like I did those old beasts of the Big 3.
FWIW the old Muncies are aluminum case and the (weaker) Saginaws are cast iron case.