We put a vacuum pump on our 468, alcohol Rupert on it. We did not pick up any et at all. The main reason we use them is to pull a little water out of the engine, although we have never milked the oil in this motor, our other sbc with a toilet, or my sbc with Rupert carb. We just have a small amount of water but not enough to milk the oil. To really see dividends with a pump usually the biggest gain is seen with low tension oil rings and getting the blowby out of the crankcase.
I bought one of the Mr. Gasket style pumps that were for sale just a while back and am going to install it on my motor this year. I doubt if I pick up any et at all. I would just like to get rid of the small oil leaks and get the small amount of water I see out. My 2 cents.
Curtis