What do I have? 1950 GMC

[thetoddg]

My grandpa gave me his 1950 GMC 250 and I have some questions.

What I do know; The truck started life as a boom truck for an electric company. My grandpa traded a motorcycle for it in the early 1970's and turned it into a wood truck. He put the duallies on it and I don't know who extended the frame. The master cylinder went out in the late 1980's, so my grandpa parked it and it hasn't moved since. It ran when parked.

My questions.
What engine does it have? My grandpa replaced it at least once and claims to have the original size engine in it, so would it be a 270? And is there a way to tell the differences between the GMC inline 6's?

Does anyone recognize the rear end? If so, what kind of gearing ratios are possible? I kinda like the dually look and would like to put a different flat bed on it.

Is the 250 a 3/4 ton?

Any other information and/or advice would be greatly appreciated. Thanks.