340 or 408?
In a car that's gonna see street duty, area under the curve matters. A lot.
Now...on a drag application, with appropriate stall etc, maybe it doesn't matter as much. But if you're going to operate over more than a 1000 rpm window, that area under the curve is everything.
I really don't understand how this is a debate.
The problem is many things are being vaguely debated and interchangeably.
1. Can a 408 & a 340 make the same power curve basically stall to shift, I believe the answer is yes.
2. Is it gonna be some huge extra effort to do so, I believe generally no.
3. What about the extra torque of the 408, if geared right (take full advantage of the power curve) they should be putting similar torque to the ground.
4. What if they aren't geared right and run similar gears in most case it seems people under gear so it's generally gonna be to the advantage of the larger cid. Which is to me generally a good reason to build larger, build for the gearing your gonna use.
5. Should a similar hp/weight cars be able to produce similar performance eg.. 1/4 mile, I believe yes.
To me that's one side of the argument can these two engine have similar performance, I believe the answer is yes.
Now will they be streetable and that's a huge question cause it means many things to many people, some might find both not street friendly. It's really up to the individual, what will they find acceptable/perfered.
Will a 500-550 hp 408 be more streetable than a 340 I'd say yes, does that make 340 unstreetable ?
A 500+cid will be even be more streetable does that make a 408 a terrible build ?
Which would I probably do, I'd just add heads to what he's got and decide after, depending how that goes.