Carb, Cam, Compression, Exhaust Manifolds

Those are the parts that added power to the 289 k-code. The other stuff just added revs to match.
Carb was bigger, 1.12 vs 1.08 as stated (the throttle bores are bigger too).
Cam was bigger, 289/"271" had about 228-228 solid duration at .050" lobe, and the 289/"225" had about 180-180 at .050", a teeny tiny cam, great for watching the fan blades at idle but not much else.
Compression was higher, over 11-1 on the early 289/271 vs 10-1 on the 289/"225".
Exhaust manifolds are also way better than those twisted drinking straws used on the other 289s.

Intake and head flows were about the same which is why the 289-K *only* made 271hp. A good intake (and heads) will really wake it up.