2008 TB SS AWD 3SS
He has 3.42s, every I6 Ive tuned around here has 3.42s except for mine and 1 other that has 4.10s.Why go 5.3L when his 4.2L truck probably already has 3.73 gears and can push 400 HP with a few mod....not to mention all the room in the world for a turbo! And yes it will involve upgrading to the I6 E67, but he won't have to pull off the front half of the motor. He will want up upgrade the head though.
I keep telling him get one of the new Kooks headers thats coming out in Jan (already ordered mine), buy an 06-07 head and have it ported, buy some custom cams, then Ill tune it for him. Should put down 400 with those, problem is its probably cheaper to drop a 5.3 in. If we can find a motor for $500-750 and a wiring harness for less than $300, we'll be in business for less than $1500-2000 all in.
One day my 02 will get an 06 I6 with the above mentioned head work and cams, I love the powerband on the I6 and how smooth that engine is.
Biggest issue Ive found with the E67 swap is the BCM/cluster/radio stuff. I dont know if it will all play nice, especially the 02-05 guys that arent CAN based and still on VPW comms.