New stage 4 clutch, replaced alternator, battery still won't charge...

 

I think you will have to provide more data. What happens when you try to start it.

 

You need to use a voltmeter on the battery while it's idling to see what voltage the alternator is charging at. Could be many things, bad replacement alternator out of the box, damaged alternator connector/wiring harness, etc. I worked on one car where I was lazy and assumed the new alternator was bad, turned out the exciter wire in the alternator wiring harness broke in half causing the alternator to not charge

 

There is a small wiring harness that's just for the alternator, it's possible one of the wires in it has broken. Unplug the little harness from the car, and inspect it closely. A replacement harness from Nissan doesn't cost very much. Have you had your battery tested to know that it's still good?

 

I had the same issue and I ran a wire from the alternator str8 to the battery and issue solved. Someone was charging 75/hr to trace the wires

 

thats cheap these days. labor rate at our shop is like 190/hr