Up to about 33 mm gap from gpu to front inner wall?
If you can dremel a 63x63mm hole in the front metal (and dont mind the hose size adapters) maybe you can fit this 38mm thick one (38x62x62).
https://modmymods.com/laing-ddc-pump-12v-ddc-1t-6500023.html
Since your RAD is top mounted and...
