look into how much a 4AG weighs and how much a 2JZ weighs
then add up the 4AG weight + the weight of the original hood + weight of battery and see if it comes anywhere CLOSE to the weight of the 2jz + FRP / CF hood
if it doens't, you'r in trouble still.
oh. did i mention the fact that you can't use the T50 tranny, but the W5x tranny with a custom bellhousing?
factor that in as well.