66 Dart, 408 runs hot. HELP PLEASE!

In my 69 with a 408, 4 row aluminum Radiator. Never gets hot. Similar Dyno numbers. Why is there no room for a mechanical fan? The RAd. you are using is only 2 row...

from the core face to the end of the pump snout is 2.5 inches. The core is physically thicker than what I had in there a few years back. I went as far as cutting out the core support mounts to gain some space, and it helped, but not as much as I was hoping for.