how to make a 6.1 spin safely 7500 rpms?

My point wasn't to dismiss the new hemi or even LS etc.. yes there great got a lot of good components OOTB. But doesn't mean older engines are necessarily inferior. If you build a 360 and a 5.7 hemi too similar specs your gonna come out with similar results.
And that really goes for any brand of engine that size.

And I disagree 340 has enough CR and cylinder head airflow to make 425 hp
If a 360 magnum can so can a 340.

And that's my main point it all comes down to heads and that's what make a stock hemi great but a 318-360 is just an upgrade away.
So really it just preference and budget.