So I have a KA24E in my S12 that I am pretty sure is from a '89 240SX.

However, I do not know a few things here...

How many liters is the engine?
How many RPM's does it redline at?
What kind of spark plugs do I need to get for it? (& Wires)

Gah, I have a few more but Im so tired I forgot... I'll post'em tomorrow when I remember them.

2.4 liters

ka's don't like to make too much power after 6000

ngk's have allways seamed to work good in any nissan motor i had, a auto parts store should be able to hook you up with the correct plugs and wires if you tell them you have a ka24e from a 240sx

So Red is 6000? Whats the max after Rev, 8000?

ka24de's make max power at 5,600rpms and redline at 6500 or 6800/6900rpms (can't remember which one) depending on which ecu you have. I think the ka24e makes max power at around 5200rpm. Not sure how high the ka24e redlines at. Either way its pointless to rev an engine significantly past its max power rpm point. High horsepower n/a ka24e's have been known to rev extremely high but these are racing engines running high octane race gas.

Good to know, thanks a lot guys.

Wait! One more question...

I'm probably going to replace my fuel pump. However, since this engine is a 2.4L do I need something different? What kind of fuel pump should I get?

The stock one is fine unless you want to go with a turbo setup eventually, then consider an upgrade.