Convert iMac 21,5 (or 27" Thunderbolt Display) to a 4K Monitor?

Apr 10, 2019
Hello, I have a busted 2011 iMac 21,5 and I'm wondering if I can buy a new 4k monitor and install it in the case of the iMac, because the case is so nice and these new monitors are ugly plastic ones.

I also have a busted apple Thunderbolt Display 27" that I could perform this operation on (but that one has less space - iMac has that bottom part)

I've bought today a G5 (made in Ireland... I haven't seen not made in China in a long time) and plan to mod it, then use one of these displays on it.

Thank you