I bet that the first thing that you think about when I say Back to the Future is a DeLorean DMC-12 going 88 miles per hour (142 kph) and hurdling into the future by exactly one minute with Einstein ...
Leaf springs lead a tough life. They are faced with the dual responsibility of both locating and suspending axles. Over thousands of cycles, leaf springs eventually fatigue and either sag or break.
When you picture a Toyota pickup truck from the 1980s, you're probably imagining the 1985 Toyota from the "Back to the Future" movies, with huge KC rally lights, a roll bar in the bed, brush guards, ...