our good friend Norselander has excellent ID pics of 55-59 chev and gmc, you can
sneak inta his garage here and take a peek - the CDN versions are the same as the US, just different series numbers [9300 = ½T]
you might have a 57 that's had the grill changed, or if you've got the original title [or it's descendent

] the truck might have been sold right at the end of 56 and first titled in 57, as they used the year of first reg back then - my 57 panel was first reg'd in Jan 58 so titled as a 58
Bill