Yes. If you are patient, you can find an X or R block for a reasonable price. I bought my last X block brand new, in the box, unbored for $800.00 cash.
A correctly prepped X or R block will take anything an LS will. Don't let the junk yard scrounges bullshit you. If you are making power with an LS, you are using an aftermarket block. Just like the SBC. My rules with SBC's was 500 HP for a circle burner or 575 HP for a drag car and you bought a block. If you didn't, it was built by someone else.
No one making big power RELIABLY is doing it with a stock block. If it was true, nobody would make locks in the aftermarket.
FWIW! You can make 550 HP falling off a log with a decent 408 and eddy heads. And that's using HRT's and turning 5500 RPM. If you don't RPM it's guts out (keep it under 7000) it will be as reliable as anything else.
