Variable Impedance Mic Pre for old Ribbon mics

[Surfkat]

I have a few older ribbon mics, a Bang & Olufsen, an EV Velocity and a Reslo. All of my mic pres are modern 600 ohm units, API 512, Old School, A Designs P1, Avalon 737, Pendulum Quartet & Drawmer 1969. All of these mics seem to have bery low gain and be noisy. I was told that I needed a 150 ohm impedence mic pre to match up with these older ribbons. Which contemporary mic pres have variable impedence for this application.