what part is it? 1950 GMC

[oldman3]

Originally Posted by Advanced Design

I believe that goes under the grill, like a splash shield on the bottom.

Doug is correct. It's a splash shield, but also helps directed air thru the radiator.
The two bracket will attach to the radiator support and the rear part of shield should also attach to the inner fenders at the front.

Pic 1 Here is one for a Chevy (different that GMC) that look similar but different.
Pic 2 here it's painted and partial installed, you can see the holes in the inner fender that will finish bolting up the shield.

Hope this helps...Jim