I plan on modifying a factory harness myself, much more budget friendly. But i also plan on using a drive by cable system, not the drive by wire that this engine originally came with. if it doesn't pan out then maybe I'll go megasquirt gold box or something. Seems to be alot of success there with turbo ls swaps.
The issue with going with an OE harness and PCM is that you still either have to spend $600 on HP Tuners to tune it, or hire someone to tune it for you. So by the time you're done, you're still probably $1k into it.