The USDM m3's only came with 240hp at the crank. 40hp is roughly what you'd lose through the driveline, give or take a couple.
To give you guys any idea of some other stock cars. . . v10 M5 made 380whp, rated at 500hp. 08 sti an EVOs make a little under 200whp, both rated at 300. We just had a 2006 G35x that made 220whp stock before tuning, rated at 298hp stock (RevUp motor). Stock 2sk makes about 185whp on the dyno, also rated at 240hp.
The power that the M3 made is about what I expected to see at the wheels. There is some discrepancy whether my VANOS works or not, I should have a touch more low end torque. I'll have to figure that out this spring.
As for the Honda head, I think it was somewhere around $3200 for the machine work, valves, seats and guides. Not cheap.