Gene,
With a very healthy 427 S/O I used a 3" thick aluminum Walker radiator, made to fit. I had a simple 16" fan, no special shrouding. I watched the temp gauge and only turned the fan on if the temp started to climb significantly. Like you, slow traffic on hot days. I didn't have problems with over heating at all.
I don't mean to be unnessecarily redundant here, but do remember that even when the gauge says 200,or even 220 you're still ok. Your cooling system is under pressure and will not boil until as high as 230-240, depending on the release pressure of your cap and what the radiator itself is built to withstand.
The big worry is getting the engine
oil hot enough to "cook" it. You aren't going to do that at 200-220. Not even close.
If you're worried about boiling over, try installing a higher pressure cap. Check with the maker of your current radiator to see what it is built to withstand in the way of pressure.
Now, if you're constantly running up in the 200-220 range, even on cooler days, you probably do have an undersized radiator/fan issue.
As to shrouding, there isn't much you can do for the low speed problem, except to get a fan or fans that give you the most coverage area of the radiator's cooling fins. At higher speed, you're not having aproblem and probably won't, because the gaping hole in the nose of the car lets a LOT of air in. That said, if you install the aluminum shrouding in the nose of the car like an original has, you will assist your cooling all around. First, all of the air going in the nose is forced through the radiator. Second, engine heat is not getting to the front side of the radiator where the cool air is. Without this "nose job", at low speed, the fan will blow the air through the radiator, it will mix with engine heat and come back around for another trip thriugh the radiator.
For me, this wasn't an issue, so I never did put the aluminum in the nose. It probably won't be for you either, with the right radiator and fan combination.
BTW, I goofed more than once and let mine get up in the 240-250 range, before turning on the fan. As soon as I did though, the temp came right back down. Even on 95+ days, mine would not get over 200 with the fan running.
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