an is200 gearbox is fine, but you need the altezza bell housing and then you will need to put the shifter mount into the second possition....(.clear when the box is on the floor)
you will need to change the oil pickup and the sump, the distributer will need removing and you will need to go for full electronic ignition as the distributer will foul on the bulkhead, there are a few other bits and bobs if you need to know, just ask
the is200 diff and propshaft can handle an incredible amount of torque and power...so need to worry there, i am still running a std diff in my car......after a Kaaz 2 way blew up!! i am running 540hp