You should make more than 408 hp , my 340 makes 412 hp and is almost stock except for some head work , air gap and cam and .30 over mahle forged pistons .
Good luck .
I've found D2000 to be really hard on heads that are "average" in flow #s.
At a guess I'd recommend adding around 20HP for any peak head flow figs below 250 cfm. Pretty rough but it's OK for a "ballpark" figure on the low side.:D
