I read an article a while back about the D50. It seems there are a
plethora of them in junkyards because there weren't any good
aftermarket upgrades available. Apparently someone (ARB?) now makes a
locker for a D50.
The article suggested much of what you said; that they are stronger
than a 44, but because they aren't popular many junkyards will part
with them for cheap. Same outside housing dimensions as a 60 from what
I recall, 44-like innerds, which means the housing is actually thicker
than a 44 or a 60. They showed a close up pic of the housing compared
to a 44 or a 60...it was purdy damn stout.