Head Games!

Race only?

12 second implies just into the 12s, with unlimited suspension, you only need a P/W of .081 to get there so, at 3400 pounds race weight, that would be 275hp

But on street tires, and with street suspension, you might need a P/W of .094 so 320 hp.
But if you want a low 12 second in street trim you could be looking at a P/W of .115, so 390hp

So obviously, each of those builds is gonna be considerably different.
@Rumble said you had some decision to make, and I agree.
Cuz 400hp in a streeter is way overkill. Even with 3.91s, if the tires hook, you can't get to peak power in Second gear until just before you are speeding. And the ride takes about 5 seconds from a dead stop. But more than likely your street tires will NOT hook,and they will spin all the way....... and spinning ain't winning.
If that is what you are after, and you have the money, I find no fault in the doing, on account of that was what I wanted, and did,lol. But I didn't have any track goal in mind.

To say it in another way, 400hp at 3400 pounds is a P/W of 400/3400= .1176, and with unlimited suspension, has the potential to go about 11.5@116 mph. But with street suspension and tires expect to be a second or so slower.

Now, to make 400hp with XJOUorZ heads
for use with pumpgas
is gonna cost you a wheelbarrow of money and and, flippin' AND; a crazy for street, cam.