NA* 1.8 motor into a NB1(1999)
 

Exactly as the title states, what exactly needs to be changed? I know this is not the ideal setup, but for reasons it needs to happen. I was wondering how that's even done, and what I would need? I know the NB's don't have a return line for fuel, and the NA's do, but I don't think that should affect much. I was thinking more along the lines of the cam sensor and such being problematic, and sending wrong signals, which would mean an ecu change to the NA8 ecu or aftermarket. Any other thoughts as to what would need to change? or what else I would need?

Where are you located?

Unless it is impossible to get an NB1 motor where you are, the time, effort, and money to put an NA motor into an NB is going to far exceed that of acquiring the right motor.

The easiest way to do this would be to use an aftermarket ECU and a complete NA engine and engine wiring harness. Splice the NA wiring harness into the NB harness somehow. You might be able to keep the NB returnless fuel system, but I'm not sure. If you go with a cheap aftermarket ECU, you're going to have a bad time. If you buy an expensive ECU, you should have spent that money on the right motor. And unless you're really a natural with wiring, that splicing is going to take time and a lot of planning.

It's not just a matter of the cam and crank sensor signals being wrong, it's that the NA uses a completely different system for determining crank and cam position. The NA relies the famous "CAS", which performs the function of both a cam and crank sensor in one. The NB has distinct sensors for each of these. The NB ECU expects to see a certain tooth pattern from the crank and cam sensors that the CAS is simply incapable of producing. Then there's all the intake stuff. I forget which intake features appeared on which years, but it's going to cause you headaches if you try to use a stock ECU.

You could put an NB1 head on an NA short block, but I don't think that's the question you're asking.