Need Help identifying year/submodel of truck of my grandfathers...

[BogeyBoy82]

I'm looking for some help in trying to figure out the year and model of the Chevrolet pickup that is in the picture here.

My granddad founded this company in 1958 and I believe this picture was taken around that time. I know what years it is around but without a pic from the front I can't tell exactly. I figured you guys could tell via the mirrors or something that may be "year/model" specific without having a full picture of the truck.

Also if anyone knows of a truck that would be a good basis for a project that is similar to this one hit me up.

Thanks in advance.