Standard FULL CAB is typically 42U but I would call it 40U. You loose about 2U of space in standard cabinents or atleast the ones I use.

Either 42 1U servers or 21 2U servers.

Some people like to leave spaces between the servers to prohibit space transfer but if its not a router or a network critical devices I dont see a reason too. Just might want to keep that into some consideration.