How long was the 351M in production and what exactly was it built for , torque or high rpm`s ?

The 351M or the 400 were not particularly powerful and both were big and heavy for their power and torque output. As cars were downsized in the mid to late 80's the 351 M was used only in trucks, with some success. The Achilles heel of the 351M/400 was its shear weight and bulk, It simply will not fit in small chassis like the Mustang without MAJOR modifications!
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