ive got a 300 I6 in my 75 f100. if you like low-end torque, stick with the 300.
ive been looking for performance parts also. so far only thing that ive found was headers, cam, and the three carb trick (which requires three intake manifolds cut down to only two runners per carb)
a.k. miller use to have a pikes peak race car(open wheel class) with a 300 I6 in it, and i doubt he was shifting @ 1500 . so it can be done.