Wait, why are you rebuilding it?
Really? Its a '98 JDM motor AND its a ej20k. Why would you not rebuild it before putting it in. 20k's are great but you are foolish to just put one in without cracking it open and taking a look.^^^+1
Yes clunking while turning is an axle issue. Try to pinpoint which side it is coming from, having a buddy stand outside the car while you slowly turn may be easiest. Changing an axle isnt really a tough task, can be done in a few hours, usually with simple handtools and a good breaker bar.I'm going to work on my car tomorrow to fix some bugs and I'll try to get some pictures in.
I'm having some issues when I turn corners. When I drive slow and go around a corner, I hear some clunking. Anyone know what that might be? The axles perhaps?