They can handle a fair amount of power, but this is very dependant on driving style. Also, depends on the condition of the box as most of them are at least 22 years old. How much power do you plan on having? I have seen over 200rwhp put through a Starion box daily, but this wasn't thrashed or flat-changed (well, not much). I have also seen a Standard Starion box do some decent laps around Eastern Creek in a Group A Starion race car :D
Please register your vehicle details on the AUSTRALIAN STARION REGISTRY <HERE>