i figured it was 38 series because of the 9 foot bed. 31 was 6 ft, 32 & 36 have 8 ft beds
US went from 3100 series in 57 to 31 series in 58 on the fender spears, not sure if canada followed suit
on the fender spears 3100 US converted to 1300 on canadian trucks, something got lost in translation at the border
LMC truck has a good
vin decoder for gmc/chevy trucks unfortunately it doesn't cover the canuck trucks
a 2 second google search gave me this at
oldgmctrucks.com
chevy 1959 3804 6 cyl serial #17774 gvw rating 6000 lbs or less