I cannot claim to know anything about Kody Swanson's anatomy. However, I believe "ballz" in this context is being used in reference to his bravery.

If this is this case, I can speak confidently of the size of these figurative "ballz". I have followed him into a corner once or twice in a Silver Crown car, and I've watched him run a pretty terrifying qualifying lap at Ocala. (I think it was quick time at a USAC show btw) They are LARGE, as in needs to have a figurative wheelbarrow to get them from home to the race track LARGE.