Here's a dyno of the 380 hp 5.9l crate actually making 409 hp add some cr and more cam might get there without porting add another 25-50 cfms to that should be no problem.
RPM | TQ | HP |
2500 | 380.6 | 181 |
3000 | 402.9 | 230 |
3500 | 415.1 | 277 |
4000 | 437.8 | 333 |
4100 | 439.5 | 343 |
4500 | 437.1 | 375 |
5000 | 416.3 | 396 |
5400 | 398.6 | 409 |
5500 | 388.6 | 407 |
6000 | 343.9 | 395 |