1947-1954 are not the same in just about all components.
You should try ID the 3100 frame year and the 3800 frame year.
"a '51 3800 truck that i'm putting on a 3100 1/2 ton chevy frame"
What parts of that 1951 3800 (1-ton) truck do you want to put on that 3100 (what year) frame.
People here can help you.
Here are 1951 specs/dimensions/etc/etc. Similar information is available for for all 47-54 years.
