The Exploding Pinto

P bought a Ford Pinto. P alleged it to be dangerously designed because the location of the rear fuel tank was such that even in a minor rear-end collision the tank would easily be pierced and explode. Two years later, Ford redesigned the car, moving the tank to the front. Four years after P bought the Pinto, her car exploded into flames after a rear-end collision, and P was badly burned. At the trial of P's action against Ford, P offers evidence of Ford's relocation of the fuel tank in the later models. Ford objects. What ruling and why?