A few months ago I upgraded to a 4 core aluminum radiator due to my stock one leaking at the tanks. Here is what I did and what I ran into for problems. I had posted this info in the "What did you to to your 4th Gen" thread. @Wild one thought I should put it in its own thread, so, here it is.
1. The ads for the radiators say it is a direct replacement. It is not. It is close, but, there are a few things that had to be modified to make it fit.
2. The radiator is about an inch thicker, so, some things need to be trimmed and/or modified.

3. The shroud will be moved back towards the engine, so, I had to trim about an inch off of the upper shroud. You see where I trimmed it in this pic. I drew a line where I needed to cut it, from one side to the other and got out the jigsaw. I could probably trim a little more off as it was still a little tight getting it back in, but, it seems to be working fine. Also, I had to trim a little bit off the shroud mounts, where it sits in the radiator, as it was a bit tight to slide into the mounting points and wouldn't fit in the mounting brackets properly.

4. The bracket for the A/C lines does not line up. I'll have to modify the bracket, maybe with a spacer and longer bolt. You can see the space between the lines and the new mounting point on the radiator

5. The mud plate that attaches to the lower shroud will not line up the mounting holes. This will need to be modified. I think drilling new holes may work, but, t may also need to be trimmed down, as the front of the mud plate will sit forward and might start flapping from air movement. Haven't modified mine yet, but, I'll update what I did when I get to it.
6. Here is the installed radiator

7. Here is the new radiator cap. It is pretty nice. Haven't had any issues with it, except I kept getting a leak at the upper hose. Seems the nipple is a fraction of a millimeter smaller than the stock one. Had to really tighten the hose clamp. Seems ok now,

While you have the radiator out, might want to flush the heater core. I did on mine.
It does take a little longer to get up to operating temp, so, took a while to get the thermostat to open to get all the air out of it. I ended up filling it, driving it, let it cool, top off radiator, repeat a couple of times. Waiting for the thermostat to open , in the driveway, took too long. Took a couple of days to get all the air out.
If anyone is doing this and has any questions on what I encountered, let me know and I'll help where I can.
1. The ads for the radiators say it is a direct replacement. It is not. It is close, but, there are a few things that had to be modified to make it fit.
2. The radiator is about an inch thicker, so, some things need to be trimmed and/or modified.

3. The shroud will be moved back towards the engine, so, I had to trim about an inch off of the upper shroud. You see where I trimmed it in this pic. I drew a line where I needed to cut it, from one side to the other and got out the jigsaw. I could probably trim a little more off as it was still a little tight getting it back in, but, it seems to be working fine. Also, I had to trim a little bit off the shroud mounts, where it sits in the radiator, as it was a bit tight to slide into the mounting points and wouldn't fit in the mounting brackets properly.

4. The bracket for the A/C lines does not line up. I'll have to modify the bracket, maybe with a spacer and longer bolt. You can see the space between the lines and the new mounting point on the radiator

5. The mud plate that attaches to the lower shroud will not line up the mounting holes. This will need to be modified. I think drilling new holes may work, but, t may also need to be trimmed down, as the front of the mud plate will sit forward and might start flapping from air movement. Haven't modified mine yet, but, I'll update what I did when I get to it.
6. Here is the installed radiator

7. Here is the new radiator cap. It is pretty nice. Haven't had any issues with it, except I kept getting a leak at the upper hose. Seems the nipple is a fraction of a millimeter smaller than the stock one. Had to really tighten the hose clamp. Seems ok now,

While you have the radiator out, might want to flush the heater core. I did on mine.
It does take a little longer to get up to operating temp, so, took a while to get the thermostat to open to get all the air out of it. I ended up filling it, driving it, let it cool, top off radiator, repeat a couple of times. Waiting for the thermostat to open , in the driveway, took too long. Took a couple of days to get all the air out.
If anyone is doing this and has any questions on what I encountered, let me know and I'll help where I can.