[thstone]

Yes, in a street car a shock tower brace can help reduce front end flex but I doubt that it will solve the problem with squeaking interior components. The root cause of the problem is cheap interior parts which loosen and the problem isn't only a function of chassis flex or rough roads, a major contributor is simple old age.

In regards to a car with a full cage, the chassis is significantly stiffened by the cage. However, 90% of the interior is also removed so there are no speaks or rattles from those components.