FWIT, my COE had a factory track width of 61.3" I have replaced the chassis with a late model with a track width of 65". The point being the factory track width leaves a bit on the table for wider wheels. Because track is measured at the center of the tires the off set per side is only 1 1/4 " in your case. I would think you would be fine but the torsion bar system is a whole different issue. I have seen many an F-100 with the Plymouth torsion front end on them and it works very well. Worst case you could but some negative off set wheels.
Rob