Overheating question

[BillyDeluxe]

Hi guys,
I have a bored 350 out of a 1980 C10 truck in my 65 short stepside. During the summer months I always have the same problems since a few years now.
Always when I get stuck in the traffic the engine starts overheating. As soon as you move again the temp in going down quickly.

What I've tried so far:
-I switched to the factory stock 3-row Harrison radiator (had something different before)
-switched thermostat serveral times (tried 160, 180 and high flow),
-switched from a 16" belt-driven fan to a 19" belt driven fan,
-tried with and without electrical fan (yes it's better with electrical fan switched on but I want to go without - it must be possible!)
-because of a blown head gasket I cleaned both heads last year and checked all the water channels - nothing suspicious
-I bought a stock shroud but the new 19" is too big for it, surprise!


What I would do next:
-I would buy a brand new radiator (maybe 4-row desert edition) - hopefully the brackets still fit for the bigger one
-I would give my current radiator away to let it clean and give it a new net
-I would swap the water pump to a Edelbrock or Stewart high-flow pump to get more flow into the system


What do you guys think - what would be your next steps?
Thanks
Andy