Towing upgrade

While touring Tassie lately noticed a couple of 79 series and 80 series cad chassis that had been upgraded to 3750 capacity and even lengthen. I inquired of one of them where he got it done, which was in Vic. somewhere. Too many Crownies, too late at night, you know how it goes. Anyhow does any one know of this being done and where it is done.

Thanks,