I think that's great.
The KA24DE has a relatively long stroke, has plenty of torque and makes the most power at about 5.5K RPM. If you are after top end power, since you are thinking about the stage 3 chip, why not add a CAM too?
http://www.datsuns.com/Tech/datsundyno.htmAs for exhaust size, Noss suggested the use of 2.5" piping and Noss has got a thread on the suitable mods for a stage 3 chip (KA24E), somewhere.

After all these mods, you'll probably start thinking about improving the handling of the car
