jus buy a gen coupe, it ill be cheaper in the long run, and you wont have to spend 3 years building the custom parts for it... gen coupes go for like 4-5k right now... these things are gonna be the future 240sx... cheap easily modded rwd car... these things will be hard to come by at some point, so miught as well get one while you can, and put it aside/ use it as a daily till youre ready to mod it.
If you REALLy wanna waste your time and money like me, ( i suggest you do not), you will need a drivetrain from an early santa fe, or later tuscon.... or going the kia route get a sorento drivetrain.... OR do something completely custom, buyt then at that point why....
You'll need to completely reengineer the rear suspension.
cutting body panels/ creating mounting space/ tub for the differential/ suspenion The rear of the frame gets real tight in the wheel well areas. You'll have to go WIDER outside the frame of the car, cant go in too much because of said frame design.
coming from someone who is currently in this mess... IT IS NOT WORTH IT, unless you love working on cars, and really want to build a project. The amount of fabrication time/ Money that is involved with this, is quite staggering. Do not let any of us scare you away from doing it. But converting these cars to rwd/ awd IS possible, but you need to create a serious plan of attack. The parts from other hyundais and kias should be able to be retro fitted/ customed in. BUT they are NOT bolt on swaps. The tib seems to have all the components/ space to have had a rwd system in place from factory, and then decided to make it fwd for cost purposes.
the most important question you should be asking yourself is:
why am i building this car/ what are its goals... are you building something for yourself, or are you building something that you hope to become popular from...
Setting realistic goals is important, not rushing and taking your time is jus as important.