Ran a MS3 on a 114LSA in both stocker and my 408 and love it. There is power everywhere (in the 408), it looks like you are still running the stock block. Without alot of work you will not fit the TSP Giant. The LSA I have on the MS3 actually made me touch a couple valves on the stock LS1 along with TSP recessing the valves in my PRC 2.5 5.3 heads so the 114LSA would fit which it barely did. Never got proper #'s on the stock motor but imagine the 430+whp region, but made 508whp/479wtq on the 408 with the stock fuel pump barely keeping up. No time for runs before I had to transfer (military), but am another believer in the MS3.

My vote is MS3