LSx Valiant Build. Take a look inside...

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.

Just a lowly 1971 Nova street/drag/autocross car that runs 9.90's@140 with a 5.3L and a turbo.
http://www.popularhotrodding.com/features/1104phr_1971_chevy_nova/
(It is now running a L33 5.3L. At the time of this article it was a budget LQ9 6.0l)
http://ls1tech.com/forums/forced-induction/1542242-71-nova-5-3-pt7675-build-now-pt88-9-98-139-a.html