Here is another valuable post from Jesse Ybarra regarding the use of off-set wheels on a narrow-track FC-150. Many FC owners ponder this question and Jesse once again covers all the issues that come up regarding these trucks. Thanks for your insight Jesse!
The following is a copy of what I previously wrote to Jim, he is also new with a narrow track:
Most new FC-150 Narrow track Owners, people that have a first edition 57-58 narrow track, have never driven their vehicle, or any FC, the narrow tracks are the best they can be, as they are. Additionally a lot of new people don't know the difference, they think they own or have a narrow track, because they compare the later 58-65 FC-150 wide track that they own, to an even more wider track FC-170. To avoid arguments, I usually avoid talking about narrow tracks on the forum, I personally like them as they are, and because one person with wide wheels driving on dirt roads at 35 mph in rural Kansas, is not likely to over correct the steering, like another person on an interstate in Los Angeles or Phoenix and hit a banked curb.
Because of the changes of our roads in our country, most cities in 1957-58, did not have highways or interstate as we know them today, as we improved the roads, in the late 50s early 60s, the instability off pavement and problematic maneuverability on paved roads, inclined higher crown at the centerline and low gutters near the curb, required the narrow track to have a lot of the necessary geometry and engineering improvements that were needed to be done, a whole new chassis, was created, with the larger wider Dana 44 axles, allowing for spring over and spring hangers, that were able to be mounted outboard the frame on the later wide track FC-150, The wider stronger front axle allowed the springs over the axles, allowing more clearance so that the wheels can turn without hitting the springs and frame at full turn, the steering boxes are different because the frame mounting location and angle of the bell crank changed also, even when the later wide track 63-65, were made they had cross steering like the FC-170, all these necessary improvements made them safer, including the rear counterweight.
Because the wide/narrow tracks are so different, any acceptable change on a wide track, will be an opposite negative change on the narrow track.
The narrow track having the springs under the axle, has the spring hangers mounted under the bottom of the frame, stock c type shackle bolts are at a disadvantage, changing them to double shackles makes roll over easier on them.
When you change to wider offset wheels, assuming the inside spacing stays the same, the centerline of the tire is moved outward, 5" to 7" for example, as you turn the wheel, more strain and effort is required to rotate the bell crank, also the width of a tire has increased causing the sidewall plies to have more area to grip, this is multiplied with low ply sidewalls on radial tires verses bias belted with higher ply sidewalls, twisting harder against the wheel mounting flange. In some cases hitting a road hazards that crack the wheels, because of the offset.
The front will be even dangerous with a wider width because of the already over cantilever effect on the spring under the frame and axle, because of the heavy cab and engine weight concentration over the front axle, any increase in width will also be very hard on the bearings of the small Dana 27 front axle.