The only thing you gain from doing an LS swap on a Solstice is an empty wallet and a sound. You can achieve the same power as an LS3 for 6,000 grand where an LS3 is going to cost 25,000. It doesn't make the car faster then doing a couple of bolt on parts. I am not sure why there is such an attraction to it. Anything over 500 hp and the vehicle really can't utilize the power because of the inability to get the tires to hook up unless you make the car look like a roller skate which is illegal in a lot of states.
Not bashing an ls3 conversion at all but I just don't see the point to spending 25,000 because of the sound the car makes. Put 4 grand into the audio system and play a recording of a V8 running. 
Why on earth would you swap in an LS3, and I say that as an LS3 owner. Cheaper options out there that'll get you close, unless you happen to have one laying around.
I maintain a nice truck aluminum-block build in the 300-350ish HP range will be more reliable than an LNF at the same power, and that's why I'd do the swap. Water pump failures every 60k miles or so? No. Timing chain worries? No. Turbo complexity worries (intercooler ballooning? Boost leaks?) Sure, if you turbo the LS and make even more power. Hell, an iron block 5.3 LM7 is within about a hundred pounds of the weight of an LNF.
I enjoyed my Kappa, but I traded it for a 5.3 LM7 pickup. 290HP/350 ft/lbs or torque, and it's run like a top, only needing spark plugs, oil changes, and one injector in 130k miles. Reliability is why I'd want to do the swap. (Parts availability a close second.)