Told ally disagree. Let’s do some math…
600 (hp) divided by 400 (CID) = 1.5 HP per cubic inch.
A well thought out engine combination can do this. This is not exactly throw together parts from the bottom of the page. I would certainly invest the biggest chunk of change at cylinder heads!
I would approach this 400 only cube engine like a small block.
The best part being is the aftermarket big block head on s nicer than a small block head. A much higher ceiling of performance.
For a 340/360 @ 1.5 multiplication, it would equal 510/540 hp. A sizable cam it will need but not streetable? Well, that’s a driver/owner issue.
This can be done on 93 pump gas.
Build wisely!