Jeff - you must have massive compression, or a really tight camshaft!!!
I friend of mine has a 13:1 compression, 509 cube BBC in his 65 SS Impala, and it runs fine on Avgas... .700" lift, 260 degrees duration, 35 degrees total ignition timing, 1150 dominator with 98 and 102 jets.
That's interesting about the corrosion. I know that methanol gives the rubber and alloy a bit of a workout, but hadn't heard the same about toluene.
Andy, there's a guy up here
http://www.redcliffedyno.com making a little over 360KW at the wheels with his XR6T. Here's a photo of it last wednesday at a Test and Tune. It's in the 12s, but it's mph points towards a high 10 in the next month or two....