Early S13's came with KA24E SOHC engines, later S13's came with KA24DE DOHC engines. The change came around 91.
The SR16 was a VVT engine, AFAIK.
Buy a 240. It's rear drive and accepts much better engines then the Prelude ever will.
AFAIK?? Like I said, I've been out of the Nissan circle for quite some time.