Another 318 build, and questions. (LONG)
You won't need anything to avoid detonation with 9.5:1.
If you want 400hp you willl NEED a single plane intake and some port work.
Despite the magazine articles findings, a 400hp 318 is actually really really difficult and expensive to build with factory iron heads.
(mine made 352hp but by all rights *should* probably equal or surpass those in the magazine builds.)
KB399's are good but be careful with the ring gaps. And if you DO get detonation for even a few seconds they're history in the making
The XE268 will run out of puff about 5400RPM but make really nice streetable torque.