My 1950 buick has the factory rad in it and its metal. Still cools the i8 just fine, then again its a real brass/copper rad.

Last rad I bought for a s-series the guy at oreillys asked us if we wanted an all metal one or a cheap plastic one. It did cost a small bit more but hardly enough trouble or cost to claim we had to search for something custom. My blazer has a metal 3 core in it and it came off the autozone shelf, hardly custom.

 

Metal for the first gen not custom built, I might look into that when this one has a problem

 

There is all metal ones for a 2nd gen also. Of course one can still go all out on a custom built one if they like throwing money away. Easier to just buy an aluminum replacement one made to fit.