Chris,

Here are some pics of the data plates off of my '59 Chev. They should be similar to the ones for your pickup.

http://rides.webshots.com/photo/2222129100098190200NVOpMN

The Serial number and GVW Plates were located on the drivers door pillar. The Trim plate was located on the firewall (you can see this here: http://rides.webshots.com/photo/2638464810098190200FcpLCV).

Photo

1959 Chevy 1/2-Ton parts for the
1957 GMC 1-Ton