I did a little price comparison between building from scrounged and junkyard parts, and buying. They say time is money, well the converse is true also.
The junkyard 5.3l truck engine costs about $1k, and the 4L80E transmission about another $1k after rebuilding with high performance friction materials just to be on the safe side, and has to be completed with a $300 controller and a $280 wiring harness and maybe an alternator if there wasn’t one still attached at the junkyard and maybe that alternator will need a bracket to be fabricated to get it away from the intake piping. The turbochargers are $200 total and will require fabricating the piping from the exhaust to the turbos and from the turbos to the intake. Both the engine and the transmission are heavier than their counterparts in the Connect and Cruise package and tip the scales at a combined 755 pounds and the total not including materials and fabrication for the turbo installation and at least one dyno session to get the race tune right comes to about $3k±, plus hundreds of hours fabricating and tuning and fiddling with the bits to get everything singing off the same page in the hymnal. Power potential is about 450-500 HP on race gas or E85, about 300 on 87 octane regular.
GM Performance Parts sells a Connect and Cruise package for the LS3 and a 4L65E transmission that includes everything except the wires to the battery and that battery, for about $12850 ±. It makes 430 HP on 93 octane pump gas and weighs about 600 pounds complete and all it requires is fabricating the mounts and exhaust and plumbing the cooling and fuel and wiring the battery. It even comes with a warranty.
Now the question becomes which is the greatest source of joy in this build: having it done and driving it, or building and fiddling with the bits to make it run right? And is there $10K worth of joy in building and fiddling with the bits?