Will it hold 4-5" to redline? If so, you are already doing better then I thought and what most have reported. I might have to reconsider this in the future as I'd like to do a low mount turbo setup if I stick to the m42 in my car.
Do you have anyway to do some PWM control? A junkyard PWM fan controller and a simple MAP or TPS vs. RPM map could get the job done. Drop the pulsewidth for cruising around to maintiain a couple "Hg under low loads then drive it 100% under heavy loads. It should help keep the heat down considerably.
If you can keep oil and fuel vapor out of the pump, there is some hope to making this work long term. I agree too, I'm not a fan of the scavenge pumps as I've had friends have them fail. Mixed flow of vapor and liquid can wreck havoc on the pumps. There are some OEM options though that should be bullet-proof if installed correctly. | 
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