1). Probably, but I don’t think this is an issue for you. 120V won’t make the slightest bit of difference, you will just need more amperes that what 230v or 380v needs to obtain the same result in the same speed/time.
The US supply is 110-130v at 60Hz where most countries discussed on this forum are 220-250v at 50Hz so check the motor can cope with your frequency and voltage range.
Some of us are using a single-phase 220-250v (motor label voltage may have a number i.e. 230v instead of a similar voltage range)
Whilst others are using three-phase 380-415v with an inverter drive (or direct if you have a 3-phase supply) which can run the three-phase motor from a 230v single phase supply. Inverter drive also know as Variable Frequency Drive or VSD or VFD or inverter drive).
Learn how to read a ‘Motor nameplate data’ it will help you a lot as it did me.
Some use an inverter drive for the extrusion machine as it is very useful to adjust and maintain an rpm for a constant flow but then you will need to check your motor is compatible with inverter feed from the motors data sheet. May be worth considering if you are attempting to use the one motor for the shredder and extrusion machine.
2). Obtain a quote here for gearmotor as it’s very difficult to find a gearbox to fit a motor at a later date: 2-3hp motor, final rpm can be as high as 90rpm or as low as 30rpm (if you’re not in a hurry).
An example of a VFD for the extrusion machine:
Other motor brands in the US: Emerson, Weg, Century, Teco, General Electric, Lincoln Electric, Hitachi, SEW Eurodrive, Siemens, Bodine.
3). Maybe this video helps explain your motor wiring at 120V: – basically you will draw more current at 120v than 220v so ensure your cable’s current-carrying capacity isn’t overloaded. https://www.youtube.com/watch?v=3llc68VvzsY
Notice this is a compact gearmotor at a ratio of 1:60 therefore 1720rpm becomes 29rpm. But this gearmotor is very small and the gears may break as I doubt they will live long given the torque required from the shredder. But it might be suitable for an extrusion machine with a VFD if compatible.