Do you really think that Dallara calculated all the assemblies, that would surprise me. At the time there were far fewer engineers than today and many sub-assemblies were designed by less qualified people, especially in a small company like De Tomaso. So I'm not sure it was an engineer who was responsible for the rear hubs.
Dallara has certainly calculated the chassis himself and we all know that it is not a model of rigidity, as what even the engineers of formula 1 may not always be skilful.
I think a torque of about 150 lb.ft is more than enough.