The 50 car engine will easily go right in your 49 truck. You may/will have to drill the bottom of the front engine mount:
See page 3 of this link. Lots of useful info here!!
Also a 49-54 car transmission will not fit your 49 truck bellhousing: different bolt pattern.
Oh, btw: the optional car rear end in 49-52? was 3.70, not 3.73. The 50-54 PowerGlide axle was 3.55. There is a
tech tip on Stovebolt about using a car axle in an AD 1/2-ton but it looks like a lot of work.
