i was thinking about this transplant myself too, for a possible future plan.
the x18xe1 seems like the easiest to swap, with its throttle cable design.
but, with a bit of imagination and fabrication work, a throttle pedal from a newer car could be mounted in, for the later z18xe fly-by function to work.
the only bit im unsure about is the wiring, as theres next to no info online about it.
from what i can tell, the ecu side of it can be wired in, similar to the x14/x16 engines. the wires are apparently different colours, but its works on the same principle.
the vss side is the bit thats confusing, as it runs through hub sensors, which i think are linked to the traction control ?
im not 100% about any of it tho, as no one seems to have dished out any real *working* information.
ive seen alot of bike carb transplants, but alot of the electronics get ditched/bypassed doing it this way, and again no standard oem ecu info.
if anyone knows, or gets any info, please share