You will need gearbox, bellhousing, clutch, shifter, slave, gearbox crossmember, tailshaft and something to cut a hole in the tranny tunnel to fit the shifter.
Cost = alot.
Don't need a manual ecu, just got to fool the auto ecu with the neutral start switch.
Worth it... Yes.
Gz20 = slow and boring
1JZ will bolt right in if you can find a JZA70 supra half cut and crossmember. If you already have the R154 gearbox then you will need a new JZ bellhousing for it.