For the H-bridge, you may use power MOSFETS such as the IXFX90N30 (available from Digi-Key...) 90 Amperes @ 300 Volts
But i do have two questions:
1 - What is the power of the motor (in Watts or HP) and
2 - What is the MECHANICAL load for the motor ?
Having a motor reversing it's rotation every 1.75 seconds is NOT a normal way to have a motor work. Okay, 120 RPM is quite low, but if your motor is attached to a 50 lb flywheel, it will last, say 2 - 3 minutes !
You will also need an electric brake to stop (or highly decelerate) the motor before it change direction. This is done by:
1 - Remove ALL power from the motor and
2 - Putting-in a high power low value resistor directly across the motor. When the motor power is cutoff, tho motor will continue to rotate due to it's inertia and thus becomes a generator. Putting a resistor will brake the motor and absorb/dissipate the motor's/flywheel's kinetic energy. Do NOT short-citcuit the motor. If you do so, the MOTOR will dissipate the kinetic energy and may become quite warm.
And if your motor's load inertia in very high, you may have to think about a mechanical brake.
Finally, if the motor's output power is low, you may advantagely consider a stepper motor rather than a DC one. Steppers ARE designed to continuously "stop-and-go", change their speed and change rotation sense.