If you want to make 400bhp, then I suggest the following:
CNC ported and rebuilt heads. I'de wait until VT Engines comes out with their stage III CNC job and see how well their results is with that.
As for Cams, I'de also wait until VT Engine comes out with their stage III cams to match their stage III cnc cylinder head job.
Second, you need to change your intake over to the Fox Lake setup, like the new one that Ken Bjonnes is using. I'm not sure if his version is available to the public yet, or if its still in testing. If it available, I'de go with that. If not, go with the P-51 setup.
Aside from that, I would go with the following in addition to what you already have listed in your signature:
Long tube Headers
U/D pullies
Cobra R u/d power steering pulley (If you can find it.)
Colder thermostat (I recommend 160* if you don't do tons of winter driving if freezing weather.)
Colder plugs (With all the mods you're talking about, I'de go two steps colder than what you have.)
Follow all this work up with a good tune. A good tune is what will make or break your combo. Once you get the tune, ditch the timing adjuster and sell it for some money.
You may also want to invest in some sticky tires and some suspension work to plant that newly found tire. Remember, suspension work is just as good as hp when racing. If you have a five speed(which, I'm going to assume you do since you have no automatic mods listed), I'de upgrade my clutch assembly, go with a ligher weight flywheel, and add an aluminum driveshaft to the mix. A stronger drivetrain never hurt anything.
Then, there is also the option of boost, which the guys above have covered quite well so no need to comment there.