Toyotas are easy and simple to get running, specially old ones.
Mercedes benz are famous for being secure even in wiring. So installing a manual box but not coding out the tcu will cause the system to lock into failsafe mode permanently.
Its not a simple taar kaato aur yahan jorr do wala case. In benz a lot of sensors are wired in series but with different terming resistors, those sensors do not cross talk or short out but their output is picked on the bus only by the control unit that wants it.
E.g. the engine temperature sensor reading can be requested by the ecu, tcu or ac panel and its reading is broadcast and picked up. The abs, ebd etc. dont care for it so dont need it. Its canbus workings. And the amount of bus traffic even in this old buzurg one here in this thread is still quite higher than new corollas.