If it is a Canadian GMC, as Grigg said, the front of the frame is the same as a Chevrolet. This IS NOT the case with US trucks from what I’ve been told. I swapped a Canadian GMC frontclip onto a Chevrolet frame with no issues. Something to think about if you learn more about it before pulling the trigger on the sale.

1970 Chevrolet C10
Grandpa's -- My first truck -- In progress to shiny
Follow the build in the Project Journal
1950 Chevrolet 1-Ton Dually
"Ole Red Girl"
In the Stovebolt Gallery
More pictures here
1951 GMC 9430 1 ton dually--Shiny! | 1972 Chevrolet C20- Rusty- the puzzle box lid for the C10 | 1962 AMC Rambler American- my wife's
Parts trucks-
1951 GMC 9300 | 1951-GMC 9430 | 1951- Chevrolet 1300