Update:
Ok so I took my truck in and had the driveshafts balanced by a more reputible company in town and wow what a difference. There is only a slight vibration now at 20Km/hr and that's hit; hardly noticeable. What I did notice though is that my springs are starting to sag a big and that could be contributing to the problem.
Certainly a lot happier with my wagon now, that's for sure.
