It does not sound like a good idea to me.
The truck will look quite funny with the front wheels sticking out of the fenders.
I don't think you will gain anything.
I would rather drive a narrow truck, they fit places you would not believe, so long as you're not afraid to try.
I doubt that you will be taking interstate exit ramps at 70 to start with? And if you are I would suggest you drive something else.

•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
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-