To get a few of the terms right
a 180SX front with a silvia back is a onevia
the Sileighty is a Silvia nose on a 180back section
BTW yes we got the CA but it was a crap version
the CA18DET in the JDM and Euro S13s was sweet..the block was a little stronger than the SR20DET but it didnt get the love of the aftermarket like the SR..so not as much stuff for it.
the Stock SR can take like 400HP on stock bottom end and live..the CA can take a little more..