I bought the direct fit Summit alum for $160 a couple of months ago for my 455. I'm staying at 160 degrees at 75-85 ambient temp with no thermostate installed.

BTW, to get 160 temps, you have to use more water and less coolant. My mix is 20% coolant, 1 1/2 bottles of water wetter, and remaining distilled water.

Also, I had to cut the shroud down a bit to get it to fit properly.