Very hard to tell by the pictures, but of it has ten lug rear wheels and five lug fronts then chances are it is a 1.5 ton.

I think you have the right idea on the engine sizes, 270 would be my guess, but I know next to nothing about GMC trucks and trucks newer than 54...

What more do you know about it?

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-