you can get the uprated syncros from toyota but it you dont get the viscous front torque splittery thing or the good transfer case ..
your BETTER OFF sourcing a st205 box - as its basically a bolt in swap
Mines going thru this now ( St205 box into st185 )
Alternatively - get a st185 group A box - the setup is similar between the two - though the 205 has a better final drive, larger gearing and no means for the FWD switch.