I doubt you'd be able to swap from a "decent" std port head to the TF 270's(and accompanying intake manifold.......well, unless you used something like the Indy 440-2D ) and see much improvement to the ET in a mid-low 11 sec street/strip combo without changing something else in the car to take advantage of the bigger heads upper rpm capability. This is assuming that the current combo is at least somewhat correct to begin with.