The U code head will go into an X code housing but won't work with X code axles. You can use U code starlet axles, but might as well swap the whole housing if you have access to the axles. Apparently you can shorten KE30 axles 5mm or so to work in the starlet housing but don't quote me on that. The driveshaft is also shorter with the U code setup.
By the way KP60 doesn't mean a lot. The last number (0,1 or 2) only refers to engine size (2k, 4k and 3k rerspectively). You need to determine if you have a bugeye, non-drop hatch or drop hatch model. Easy to tell, bugeye is round headlight, non-drop has the hatch cut off above the tail lights and the drop hatch has the hatch coming down between the tail lights. Drop hatch has the U code, the rest are X code. However, there is a rumour that some drop hatch KP60's still run the X code.
Callum