IIRC, from when I was thinking of buying a used C5 Z06, Corvette has some pretty fancy sodium cooled valves. I think the Z06 had a redline of 7500 RPM, too. I love Corvettes, but ultimately, the engine displacement was just too high for me to justify. I like hanging in the powerband, and on an engine with monster displacement, you can watch your fuel gauge drop pretty quickly.
I have a lot of respect for Corvette's and the LS engines, but if I were to pick an engine for a supercar, I would look at (in this order):
1) power (~500+ HP NA, with good RMS torque and a near linear torque band)
2) engine life (no cosworth F1 engines
)
3) HP/engine weight (power to weight! power to weight!)
4) HP/unit displacement (efficiency)
5) cost
I don't know enough about the Lexus V10 to compare it against the LS engines, though... so it's just a list.
Formula engines still make me drool, with their pnumatic valves and 19,000 rpm redlines, despite their short lives and pricey rebuilds.