VC commodore above is right, use a small drill bit in the center of the spot welds, drill thru both panels then either use a bigger drill bit or a spot weld drill bit and drill thru just the old panel. Always drill from the right side where possible, from memory u shouldn’t have an issue getting to every spot weld. Prob been 12 odd years since I’ve unpicked one but was accessible with a drill easy enough.
You will need to take a lot more than just your radiator off tho.
Use a hammer and chisel to separate the 2 panels and after you fit the replacement in place, screw it first and assemble the car, fit headlights and everything, adjust as needed.
Then plug weld all the holes only taking a few screws out a time.
There’s a lot more involved but you should research a bit before doing it, like removing paint to get a clean weld, using weld thru primer between the panels and I’d recommend painting it the new colour prior to fitting on the car cause you won’t get to all the insides easily after it’s welded, you will still have to repaint but it will be easier and be a longer lasting paint job. I assume you know how to paint and prime, cause that’s important too.
