toomany2count is correct. The bigger fenders are for the bigger tires on the big trucks. I had the SAME situation when I got set of fenders for my 37. I think the opening is around 2" wider maybe more.
I am NOT sure but I think your right that the fenders are the same on 1/2 3/4 & 1tons.

Strange thing is I bought my "big" fenders from a guy in Ca. and when I realized they were to big I bought some correct ones and sold the ones from Ca.to a guy....yep, a guy in Ca.


1937 Chevy Pickup
In the Gallery
1952 Chevy Panel
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1950 Chevy Coupe
Pictures!

I'd rather walk and carry a Chevy hub cap than ride in a Ferd.
I can explain it to you, but I can't understand it for you smile