Mopar Muscle Association UK

I've used them, when I had too back in the mid eighties when I worked for Firestone to be honest they worked better with a smaller (narrow) tyre, as the tyre width increased the would become less accurate the same but would/could get you out of trouble.
Personelly I would try and find some firm that could balance them for you. Maybe even an on the car balancer or alternatively find a supplier of balance powder which is commonly used in truck wheels which may work due to the size of your rear tyres, the only downside to using powder is you have to use a dry air supply as the moisture could effect the powder.

Thanks Guy, I'll keep this as a last resort then!

Yes used one/or one very similar to balance Dave Wilsons Slicks on his TMD and they were 36" tall

But they don't balance the wheel dynamicaly and only around the circumference not side to side of the wheel tyre combo. When you have your wheels balanced professionaly they put weights both sides of the wheel (inside and outside)?