NA builds. How far to go?

[Bean]

I would go for headwork. Have a look at threads from oldeskewltoy.
Going beyond 160 can get costly quick.
Also a lot of the exhaust headers and system available are made for powerfigure upto 160 or 200+. This is mostly du to the fact that to get 180 is the same 'cost' as 200 and more (almost everything will need changing or work).
40mm crank is fine as long as you keep the revs down (below 8k).
Stock valves will also be fine for 160.

As you still intend to keep it on the street I would stick to some mild cams. As it will be a lot more drivable than wild ones.
With this engines pushing the power to the limits = loosing low end torque.
Staying within sensible figures will likely result in more fun.
Somewhere burried in here there are some dyno graphs http://www.aeu86.org/forum/Thread-Surreptitious

Happy hunting.

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EDIT: only reason to go for ITBs is sound, you wont get any performance out of them in 9 out of 10 cases and more likely to loose torque.