I think people that convert use parts from turbo MkIII/MkIV Supras. The N/A transmission in the Supra is the same one thats in the 5 speed SC300s, but the assembly between the turbo and N/A cars is different...push vs pull type clutch IIRC, so the slave cylinder has to be from an R154.
I think the 1JZ-GTE and 2JZ-GTE Soarers overseas came with R154 transmissions too.
__________________
ASE: Brakes
Yea..that very well could have been the most retarded idea I've ever heard, but .. do it anyway. -TheShow50h