The valvetrain is most likely going to end the party, but GM did it right with shaft rockers(T&D seems a good bet as GM has fitted a crate engine with T&D before(LSX454R)) Ti valves and ovate wire beehive springs.

Here's the assembled head propaganda from GM(I called Scoggin-Dickey roughly 2 weeks ago and GM didn't yet have a price ... "Much" is my guess):
Fully machined and assembled; 449cc intake port; 161cc exhaust port; 70cc combustion chamber;

2.450"/1.800" titanium valves with 5
⁄16" stem OD; Ovate wire-type beehive valve springs with 1.589" OD
(large end); Steel 10-deg. retainers with 1.115" OD

On Edit: We turned a hydraulic roller cam motor 7900 RPM for more than 100 1/4 mi. passes without issue. It was an LS with turned down valves and was otherwise remarkably stock, with only pushrods, PSI beehive springs and help from a guy that has hammered the OE parts. Stock rocker arms with upgraded trunnions, partially shimmed stock hydraulic lifters, and other stock junk. It sounded fine for short bursts at well above 7500 RPM, and if I knew what I was doing I might have dared to push it to 8,000 RPM.

The heads look like nice pieces. Here's a pic and flow data: