I used a Flex-a-lite " pusher" type electric mounted on the outside of the radiator, and kept the belt drive fan on the inside. I am running a 327 SBC, and there is not room for both on the inside. I am using the stock '40 radiator which I had rebuilt. The electric fan is on an adjustable sensor so it doesn't kick on until 190*. Cooler months / evenings, electric hardly runs. In the summer, especially in traffic, electric is a must - keeps things under 200* at 80*F in stop & go traffic. Only issue I have is if I run the truck on the freeway ( stays cool ), then come off the highway into bad traffic - she heats up pretty fast, and even electric fan has trouble keeping cool.
