Sometimes its just easier moving the wheel opening.

On my 49, I moved the wheel opening on my front fenders 1 1/2" forward on the fenders. The other option would have been to recess the firewall another 1 1/2" to 2", move the cab forward, then probably end up shortening the frame another 2" so the spacing between the cab and the bed remained correct. Moving the wheel openings on the fenders was an easy choice. On my truck I didn't shorten the frame (it was very well done), but the wheel base is correct according to the wheel base of the original frame.

If you look at straight on side shots of a 48-53 Dodge pickup, the tires are not centered in either the front or the rear fenders. Really, most people don't notice. The tires on my truck are pretty close to being centered in the wheel openings.

Things like that are things most people don't notice until they are well into the builds, if ever. Its people like us that notice, but once its pointed out, its hard to be unnoticed. Until we forget....