Not so much modify as careful selection of parts. My front end has tubular uppers and a first gen viper brake kit from AR engineering which uses drum brake spindles. They provide a narrower track width than the mopar disc spindles and allow this tire/wheel setup without any cutting necessary or rubbing at full lock.
The back has a roadrunner rear end which is wider than the A body unit allowing the 6.25" backspace on the wheels. Otherwise just some careful peen work inside the fenderwell so that I could lower it and its all good! I knew a 9" wheel wouldn't fit, hence the somewhat odd size of 8.75x18
Tires are BFG 245/40 and 255/40 respectively.