What car did the '90 motor come from? You can run the VIN to find out if you don't know. First of all, I hope it's a turbo motor. For the "dust shields" or starter plate, like people have said they differ FWD to AWD, not '90 to '91+. So if your engine came from a FWD car, you need to swap out the upper and lower starter plates from your gvr4 engine or another AWD motor. I believe non-turbo also differs from FWD turbo starter plates. I assume you already know that you need to run the AWD flywheel. Your mounting brackets are also different if this is a FWD engine. Make sure you use mounting brackets from your original gvr4 engine, especially the front because that one also differs from the 1g AWD TEL.
You definitely want the '90 oil cooler, water pipe, and lower housing like you said. If your gvr4 still has AC you need to make sure you have the right sensors. If not, it's not as important. But here's what you need to know: There is a larger sensor on the front for engine control, and it's important. There's a smaller one on the front for your coolant temp gauge on the cluster. Without A/C that's all you need. With A/C you have the larger white connector, and one extra sensor on the back. On your '90 housing, there will just be a bolt here. If you have A/C, take out the bolt and put the sensor in there. If both housings were working properly, that should be the only thing you need to do. I should also mention that your thermo vacuum valve is not important unless you have some reason to keep all of your emissions equipment and vacuum routing stock. I'm pretty sure the only line that comes off the front of the housing goes to your turbo.
So in summary, make sure you the starter plates/flywheel cover, flywheel from an AWD car, as long as the engine brackets. The front bracket must be from a gvr4. You don't need to mess with any of the '90 thermostat housing stuff(except switching the upper so you can run the gvr4 radiator), but if you have A/C you need to remove the bolt and put in the extra (gvr4 specific) sensor. The '90 cooling stuff is cleaner, and more desirable so running a '90 engine should be good! I think there's a small t-belt pulley difference and maybe differences with the oil pump, but you don't need to worry about those here. Good luck!