in japan they did not only have rs/ls/gs/gsr/itr models
there were versions with single cam engines
even there the itr came in a 4 door version and like said the gsr motor had a a;utomatic tranny as well

for the itr engine they run a slightly higher compression engine, as well as have higher octane gas more readily available

they HAD less emission control then us, and had more freeier flowing oem parts (ie header, exhaust)

JDM-japanese domestic market

jdm engines are readily available, and the reason they dont want those engine here are
1)smog emissions
2)no way of tracking where you got it (no vin codes)