RGG,

Some clarification:

Thread title:
"'51 3600 GMC"

Denny's statement of fact:
"If that's a GMC, wouldn't that be a series 150 rather than a 3600, which would indicate that it's a Chevrolet?"

Your statement of fact:
"The truck is a GMC and its a 3600 as indicated on the side of the hood and it being a 3/4 ton truck. So yeah im sure its not a Chevy."

Most likely you have a Chevrolet hood and side-emblems; or, you have a GMC hood with Chevrolet side-emblems.

What does the emblem on the front of the hood look like?

As you most likely know, the
1951 Chevrolet truck grill looks like this, and the
1951 GMC grill looks like this.