I went through the same thing trying to find a mounting system I liked. I ended up looking at Kirkhams cars to get some ideas. I have a Spal fan and will use their 1/4" gasket they recommend for the 16" fan. Then I made drawings for the fan supports and Kirkhams cut them out on their water jet for me. You could cut them out with a hack saw.
Here is a picture, but they are not bolted up yet. I got distracted on other parts of the car.
