Which PCM to choose?
With a stock LS3 throttle body however, you're limited to 1MB LS1 or E40 as there are very few 512kb OSs with DBW (except Vettes). Please make sure you are using a correctly matched pedal assembly otherwise you will get a dead accelerator pedal and a REP light.
Me personally, Id use a 1MB LS1 and either a Vette or truck OS. A truck LQ9 OS (Silverado SS, Escalade) would be an easier base to work from.
For swaps, I highly prefer EFILive over HPTuners because you can set the VIN to match whatever vehicle you install it in, plus if an OS doesnt work exactly how you want it to, you can just flash another one in (and not pay another 2 credits to do it). Not saying it cant be done, it can. If you end up paying someone to do the swap, it probably wont matter unless you need the VIN to match your car for emissions.

