3.5 vs 3.6(964)

[mcfoo]

I'm confused so perhaps some of you can shed some light.
I want to build another motor for my 914-6 race car but can't decide which one gives me the most bang for the $$$.
If I read B. Anderson's book correctly (3rd edition pages 180-183), Jerry Woods using Weber 46's and twin plug on both was able to get almost 100hp more out of the 3.6(964) versus the 3.5.(Carrera based).
I know there are other variables involved including but not limited to: exhaust, cams, valve size and porting, ignition , etc but can these variables add up to almost a 40% differential in HP between the two motors with only a .1 diiferential in displacement?
Your input and experiences building either or both of these motors is appreciated.
Tom B.