Dan,
Your question is not unreasonable. I have a 1954/55 GMC 350 COE and it has a replacement 270 engine (and, I think it had an optional 270 as the original engine).
Your truck might easily have had a replacement over the years.
Good luck on finding it has a 302 - that would be nice. The 270 is also a fine engine (and, there is nothing wrong about a 248 - just less power).
