[rubjonny]

Sounds like the fusebox is from a different year, the early ones (pre 1989) are different to the late ones (1990+), you'll need to get the right fusebox holder for the fusebox

If the donor car has different electrics as above, then ideally you want the right ignition switch & housing although it shouldn't be difficult to splice the wiring to your switch.
Rear lights should be the same, unless the Jetta had euro bulb trays, in which case you'll need to either splice the wires to your existing lights or get Euro tail lights
you need the digifant fuel pump as the CIS pump works at a different fuel pressure.
You can get rivit tool, not sure about plastic ones but you could get some metal ones & paint them black?
Hope some of that make sence to you

 

[rubjonny]

Yes you will definitly need the main pump (from under the car), I think the lift pump (in tank) is the same between CIS & digifant but don't quote me on that, you might as well fit the digifant one now you've got it

The Euro rear lights are slightly different to US ones, there are places that sell them but I'm not sure where you would find any? Someone will know

I also have a feeling that all US Jettas had Euro tray holders and US Golfs have the plug in style bulbs. Not sure where I got this crazy idea though