Yes belt driven vacuum pumps can help you make more horsepower, but....
They really only have much of an effect at good RPM, they are impractical on the street, the air you suck out of the crankcase needs to blown into something, to catch the
oil you're pulling out with it. They really have a greater effect on motors with low tension piston rings which wouldn't seal right without the crankcase vacuum. Mostly a drag racer item. You wouldn't want to run it off the driveshaft because it needs to be coupled to engine rpm, not vehicle speed. Just get a dry sump oiling system, the benefits are much more numerous, and you'll pull crankcase vacuum as well. If you have a money tree that is.