if you are going for an all motor build you are starting off great. be very careful over there in NP though... they are training cops to think that import=stolen engine.. and if you don't have the paperwork or at least something to prove that engine is yours... then you might be looking at some impound fees to cover.

as for your sons car, i'd definately recommend the P&P on the head, just to get that flow your increasing from the block... out. The LS heads are notorious for having horrible flow characteristics, so doing something like a P&P would just be another step on the right path.