The Next Brake Upgrade!

[Astromic]

Hi guys,
I'm in building my 1776 engine in my superbeetle, it will be a daily driver, and mostly a highway driver in a road with no speed limits , so a ~90 m/h will be my cruising speed most of the time.
but all i did now is engine upgrade and suspension and i will start upgrading my brakes after that to handle the high speeds, my bug is a '74 super beetle with a stock front discs and stock rear drums,...
now i have some question i need u guys to help me in;

First of all, i searched in couple of sites for a bolt-on system, i found on aircooled.net that they got an upgrade kit to the superbeetle wich contains mostly gia stock parts and they say that it is a conversion upgrade from drums to discs and that confuses me, becase all i know and all i saw is that the superbeetles come stock with front discs(including mine), and i thought i just missed somthing but what is it...

My second question is about taking any system from any other common car(for easy spar parts), not porsches or somthing fancy like it, because where i live there is not much porsche around, so i thought that i could take a brake system from any other widely common car like Civics, Collolas or BMWs(for easy spare parts and easy wheel fitting too, as they are mostly 4X100, so i'll have a wide range of wheel to choose from) , and build the adabtor beackets myself, any tips and advices?.

My last question is why we all need to upgrade to a bigger system with bigger calipers and wider rotors, and why couldn't we just add a servo(vacume assist brakes), and save of the headache ...

The reason i asked this questions because i know nothing about brakes, just engines and engines , so please support me with any tip or advice i might need.

Thnx in advance, any help will be appreciated...

Michael