I use an old Babson Bros BB4, They eventually became Surge. It is a piston pump and gives me 26-27" vacuum. I have no specs on how many CFM it moves, but it does well on 400 taps, hopefully on 500, which I should get it in 2021 0r 22. If it needs more CFM when I get to 500 taps, I can just put the next larger drive pulley on the electric motor. It does not struggle, flip the switch and the rpm's seem to be there instantly.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.