rruff
Explorer
If I remember right, when the Tacoma was introduced, the frame itself was modified to a much lighter duty compared to Hilux's.
The frame was made open C on the rear, compared to a torsionally stiffer fully boxed frame like all Toyota trucks had previously. It was supposedly done to improve the ride. It isn't necessarily lighter duty. The current US Toyota frames are apparently strong enough for people to overload them and then thrash them offroad.