Throttle-body Fuel Injection works better in two ways:
1. the engine will run off camber (on steep slopes) without loss of fuel flow caused by the carburetor's float valve.
2. Better gas mileage.
The Multiport fuel injection is available only on the 16-valve engine. While the block is the same for both engines, you would need the 16 valve head, the intake and all the electronics to make it work - which is a lot of work. If you have the TBI, the harness and the ECM, then use it.
You CAN use the Sidekick transmission (five-speed?) but you still need motor mounts. The advantage to the Samurai transmission is that there is only one style as the transfer case is divorced on a Samurai. In order to use a "Trackick" transmission, you would need a 2wd unit which would be hard to find. A three-speed 2wd unit also can be used but again, the problem is finding one.
The Samurai 1.6 adapter kit is simple, complete and costs under 200 bucks. Most of the offroading vendors like Petroworks and Low Range Offroad and others sell them.
The carbureted system can be easily adapted to the 8-valve head as the 1.3 intake bolts right up. It is only a matter of installing an aftermarket carb (My-Side seems to be the current favorite because it is complete and service after the sale from ZOR Zuks Off Road
better than what you would get with the second choice - a Weber DGAx32/36. If you call Zuks Offroad , tell them Ack sent you. That'll be good for a laugh!