If the goal is eventually turbo, why not just use the 5.3l LS4 exhaust manifolds and route up and in front the steering box.
Left side(front) W-body 5.3, LS4, Grand Prix GXP | Monte Carlo SS | Impala SS | LaCrosse Super.
- pn#12569073 (this setup requires 2 of these manifolds)
This is LS1Nova's 900+ RWHP setup over on LS1tech and yellowbullet, pro-touring, ect.
F-body alternator & bracket, waterpump and balancer.