hay matey use sunny struts ,magna discs, girlock calipers...
this set up will suprise u with better braking then a new commodore
as for stumpy why ???
they are weak as... u are better of using longer box who cares if it sits further back..its actually more comfortable.. if u are gona use stumpy skyline box model is mr30 skline.. and im pritty sure it does fit with no cuting tunnel .. i dont no i used the ca18det box the one that came with the motor..
ps if u gona do big mods and drag this thing on the streets i would go ca18det box.. much stronger... u wont regret it