This whole thread has come a long way from the original thread. Glad to see people taking intrest and going beyond the initial topic. So... My thoughts on the oil cooling issue and header wrap.
Header wrap
can get soaked in oil and /or gasoline and will burn as Mr. Knox suggests. The theory of keeping the heat from the headers away from the engine is valid. Perhaps just wrapping the pipes where they are closest to the engine may be of some help. Heat sheilds made of aluminum could also be of some benefit. Similar to the aluminum heat sheild we used to put around the small block Chevy starter motors.
I would debate the effects of drag on the car vs the speeds that are run. I don't think overall speed of the car itself are reduced by very much if any. The pull type fan (mounted to the rear of the cooler) will likely help with more air flowing through and around the oil cooler. Whereas, the push type fans (because of the shroud) will block some of the cooling air that could be going through the oil cooler. So, I think the pull type fan is the better option.
As Gimpster pointed out, we do not get near the humidity or hot temps up here in the northwest that some of you get in the summer months. And, most races tend to be run in the late part of the day and evenings. The engine temps will still get high, but likely not as hot as say someone running down south in the middle of a hot afternoon. Letting the engine idle with the fans running will be of better benefit than shutting the engine off and blowing air over the engine and /or through the oil cooler. Some people use an external fan (as Dave did, and suggested) to blow air around the engine (especially to the firewall side of the engine) during the race to help cool the part that doesn't see as much air flow. I think Gimpsters anology to tempering steel is a good one; and not far off base.
As for oil coming from the vent; Have you tried putting a loop in the vent line? Just a simple loop of tubing of the vent line between the engine and the breather. Mount the breather as high as possible with the loop slightly below it.
My two cents for what anyone thinks it's worth.
Steve