Cooling problems

Here is what I found with my car that had the same problem exactly. My radiator had swelled tubes from the cooling system being over pressured. Aluminum radiators are noted for that when you blow a head gasket while under boost. The instant pressure will swell the tubes and shut off the air flow. This also happens if water in the radiator freezes over the winter. My Duster did the exact same thing as your car does.

We had a Chevy here and it too would over heat . It had a v-belt pump with a serpentine belt system which had a reverse flow pump.

But I would check your radiator air flow with a piece of paper on the front. I also made a air dam just as you did even put a bleeder in the pump I tried it all then I bit the bullet and bought another Be-cool rad.

Here are pics of the air dam and the petcoc bleed I putin the pump before I found the bad radiator. It had a big core rad with twin fans and still would climb to 240 in a couple minutes.

I should have known it was the radiator because I could shut it off and run the fan and pump and it would still take a long tIme to cool down.