As long as he needs to buy aftermarket tubular control arms, why not buy the 5/8”?I don't believe that you can swap just the ball joints in the same control arms.

5/8" Ball Joint Impala Lower Control Arm - Speedtech Performance USA
Stamped steel factory lower control arm assemblies do a great job of keeping the car off the ground. Outside of that they don't do much for your car's performance. Speedtech Performance Tubular Control arms are designed to meet and exceed the needs of your performance automobile. Tubular...
