An OBD1 ecu will work fine. Any s14 ecu after 95 and before 97 will work fine really, you'll just have a check engine light if you use and AT or OBD1 ecu.
It's easiest to use the ecu out of a zenki, because there's no real reason to use one out of a kouki when zenkis are readily available on ebay and the forums. Plus you have to do a little wiring to use one in a 96.
http://zilvia.net/f/sale-items/88052...-obd2-ecu.html
see if that one is still for sale.
If you can't find an obd2 one, any zenki will do, but only obd2s will pass emissions.