The standard car and 1/2 ton truck rear end in 1949 was 4.11.
There was an optional 3.73 car rear end in 1949 - the 1/2 ton truck did not have an optional rear end.

http://chevy.oldcarmanualproject.com/chevyresto/4924.htm

http://chevy.oldcarmanualproject.com/chevyresto/4973.htm

The car wheels/axles were 5-bolt and the truck were 6-bolt. Jim Carter used to have a tech tip on doing this swap. I dimly recall that he suggested using earlier car 6-bolt axles. Maybe someone will confirm that the torque-tubes are same/different lengths?