What intake/fuel delivery system you run is almost entirely up to you, with the caveat that with a wilder cam, you will likely have to use either ITBs or a carb setup that is similar (Webers, Mikuni, etc, with a single throat per cylinder).
Alot of it comes down to budget. If you don't want to drop alot on fuel delivery, go with roundtop SUs that are properly sized and tuned. If you have a bit more $ to spend, go with mikunis or webers. If you don't care how much it costs, and just want it to run awesome all the time, get a EFI ITB setup.
Your headgasket/decking/shaving question is really dependent on what octane you *can* run. I honestly have no idea what they have in SA. Generally people here run in the 9.X:1 range for performance NA L series motors, and advance the ignition a fair bit to compensate (30-35 degrees seems normal). L series engines don't really like compression beyond that for street gas. http://www.ozdat.com/ozdatonline/enginedesign/ is a great starting resource for any build. If you want to go turbocharged, 8.5 is generally considered good for a low-medium boost street setup. Some guys on here though that are going for stupid amounts of power are running down into the 7.5:1 range.
As for the amount of headwork that should be done: As much as you can afford I'd say. There are some NA Z cars out there making *very* good whp/L numbers because of the amount of headwork that has been done. At the end of the day, air + fuel is what makes all the power, so the more you can get into the chamber, the better.