Nice looking engine!
You absolutely need a shroud or a full size fan. Or a mechanical fan with a shroud. Only way to keep it cool at idle with no ram air.
Also, I can see that your radiator cap doesn't vent into a reservoir (from what I can tell) The reservoir is an important cooling component. As the coolant thermally expands, it vents out the cap into the reservoir. When the engine cools, the coolant cools and becomes less in volume. This induces a vacuum in the system and draws the displaced "extra" coolant from the reservoir back into the radiator. Your engine ends up sucking air instead and you've blown out all the "extra" coolant onto the road. So you're running your radiator with a quart or more less fluid. The top 2 or more inches of the radiator are probably useless.
I have an A body reservoir and I was in Budapest a week ago. Damn shame. You can adapt damn near any unpressurized style reservoir tho. I built mine from aluminum.