Your 78 has narrow track axles. They went to wide track in 82. Getting a set of wide tracks is the first option. Even better if you get some out of a 4cyl Jeep that would have had 4.10 gears in the axles.
Option 2 would be get a set of full width axles such as Dana 44's, Ford 8.8 or 9", etc... If you want to go big then a set of ton axles would be in order.
Option 3 would be wheel spacers or backspaced wheels. I would personally prefer the backspaced wheels to the spacers. Thick spacers are pretty pricey. Backspaced wheels would accomplish the same thing, but also give you the opportunity to put a new look on the Jeep. Black rock crawler steel wheels would be a good choice.
You should post pics ASAP.