another 360/408 over heating

No my cooler is mounted by brackets and bolted ain place. It's a very solid install. My first thing at this point is to see If this engine will run cool with the flex fan. If it does not then I'm going to have to tear the heads off and find what is causing this. If it does cool down then I move on to figuring out what I can do to make electric fans work.
Rod
I forgot what kind of fuel are you running?