From your picture, looks like the you have the AG400L/Pete Low Air Leaf suspension. I always just tighten shock nuts with an impact. No hex on stud to hold the shock. No torque spec on them, supposed to tighten til bushing is same diameter as washers. Must have minium of two two threads exposed also. Pipe or strap wrench would work in a pinch as suggested by @God prefers Diesels .