The carb base gaskets will not cause a too rich condition. Verify oil level again. If you have a tach, you should see that the rev limiter is well over 5K RPM. A clogged fuel filter could cause a lean condition at prolonged high RPM. The white smoke is probably just steam... normal in the winter. Of course, if you have a bad head gasket, bets are off, but I would think it's OK, since you have good compression. Wouldn't hurt to pull the carb and drop the bowl to verify float height.
In general, if in N, don't run above 2K RPM, as you could damage a connecting rod, since the motor is not loaded.