I didnt read the whole thread and I would never consider spending $1600 on a rb then dumping more money into it. let me just throw out these options since bang for the buck seems to be your priority.
LM4 aluminum 5.3 L V8 + ls6 manifold + T56 6 speed approx. $2,500
1jz-gte + 5 speed approx. $1,600