So I have read through many pages of info and have confused myself

I just need someone to set me striaght with some info very bluntly if you wouldnt mind :P (which im sure someone wont).
Basicly I'm looking at gaining not so much morepower but more grunt outta my A12 or A14. Now I'm not familiar with these motors so i will opps up with info :).
So basicly A which motor will poduce a smoother drive (guessing the A14) and how do i go about doing this?
I already have extrators on the A12.(will they bolt up to the A14?)
What is the most suitible sized Barbies for both motors?
Would I be better going a twin Carby setup?
What is the most optimal size exhaust for both motors?
thanks guys i appreciate any help
Ron