There's no way to know from an objective standpoint . . . this depends on the design of the grounding wires and traces inside both your receiver and the phono preamp, and the resistance of the ground conductors in your interconnects and their connectors.
But there's no harm in trying it . . . and if you get a hum-free connections, you're fine. If not, you can make an adaptor with a short piece of wire, and a machine screw, nut, and washer(s) to make the connection between the wire and grounding lead (fork) of your turntable - this should leave the turntable leads completely unmolested. If you're a perfectionist, use brass or stainless-steel hardware, and wrap it in electrical tape or heat-shrink tubing to prevent errant shorts.
Also, the output cable of the MMF-5 IIRC is somewhat sensitive to magnetic coupling, meaning that if you get a bit of hum, try moving the cable around to minimise it.
But there's no harm in trying it . . . and if you get a hum-free connections, you're fine. If not, you can make an adaptor with a short piece of wire, and a machine screw, nut, and washer(s) to make the connection between the wire and grounding lead (fork) of your turntable - this should leave the turntable leads completely unmolested. If you're a perfectionist, use brass or stainless-steel hardware, and wrap it in electrical tape or heat-shrink tubing to prevent errant shorts.
Also, the output cable of the MMF-5 IIRC is somewhat sensitive to magnetic coupling, meaning that if you get a bit of hum, try moving the cable around to minimise it.