LSx Valiant Build. Take a look inside...

He was putting the final touches on a Trailblazer. 408, 12:2.1, aftermarket heads...over 600RWHP....under $10k.

Bottom line....I don't have the apparent deep poctets that you do....
You can do it WAY cheaper. The last one I built was a lq9 for $900. Sent the heads out for CNC and quality rebuild $1300. Big roller cam $350. Trunnion kit $80. CTS lifters $150. Used Hi-ram intake with throttle body and injectors $900. 539 HP @ the wheels and runs 10.6's in a full street trim Regal.