Hy rippintare, your serial number breaks down as follows
9 = 1949
15 = Chevrolet, 2 ton
43 = chassis with cab, 161" w.b.
1543 = model number
09380 = regular production number
As 31,32,33 has said, your pictures indicate that your engine has been replaced with a newer one, it could be a 235, or 261, as 31,32,33 has said, hope that helps.
