What does not match?
It looks like a reasonable match to me (but, I could be wrong - someone will most likely correct or confirm).
9HP I 15712
Vehicle Serial Number for a 1950 truck
9 = assembly plant = Norwood, OH
HP = 1950 3100 truck
I = 9th month = September
15712-1000 = 16,712th 3100 truck out of that plant that year
HBM45758
Engine Serial Number for a 1950 truck
HBM = 1950 216 engine from Tonawanda, NY, installed in a 3100 truck
45748-1000 = 44,748th engine from that plant in that year
http://www.1954advance-design.com/chev-specs/1950-Chevrolet-t-ser.pdf