Webers: yes with the right manifold to suit the round port head, may need to review the jetting somewhat to suit the stock engine. Normally you upgrade the head and cam to work in hand with sidedrafts.
Manifold: No, the head will need some serious port work if it's a stock A12. The manifold is suited to ported H89, H75 GX.
Extractors: Yes.
Which item do you want a price on? Send me a PM of you like.