Not suprised from low down with an a15 smallport head single weber, and 670kg's or something like that!?

A good cam grinder will be able to gring a cam to make power were you want it.

And a good head guy can port a head to suit your cam.

and its hard to tell is tat extracto all into one, or 4-2-1.
4-2-1 would be Ideal.