All kidding aside. A junkyard 5.3 or 6.0 freshened and opened up ring gaps - $2K; used 4L80 and converter or turbo 400 and converter - $1500; turbo and related parts and fuel system - $2500 = 6-700whp. Swap in a Lil John's stage 2 cam, Pac 1218 springs and add 100-150HP for another $600.
$8K is plenty of money to get it done.
^^^this post nailed it.....only thing I would add would be to start with an 2004 or 2005 4.8 or 5.3 with gen 4 connecting rods, be sure to buy a quality torque converter (ptc or circle d), and spec out a T6 turbo from VS Racing.....something like a S480.