This will require access to a 3D printer as well as doing a slight modification to the camera to make room for the wind knob. If you decide to use the original Polaroid back, it will need permanent modification so it won't be able to use pack film anymore. Otherwise, you can 3D print a back to work with this conversion.
Download the 3D files here and print 3 spools and one of each of the other parts. The knob and drive spool should be printed with 100% infill for strength, and the back should be printed with supports everywhere. You will need to sand down the spools and receptors to 600 grit to reduce friction, as well as any place the film slides along. The film pack is designed at 89.5mm, but printers will often add .5 or so mm to the print job and it won't fit until it's 89.5mm wide. Same with the pressure plate. Be sure all parts fit OK without forcing them. The hinges and latching hooks on the back will need filing to fit properly, and the drive shaft hole in the side of the pack will also probably need filing so the shaft fits.
A Polaroid back has lots of things in it to make it work with pack film, most of which needs to be removed to allow the 120 film spools to fit. It's easiest to work with a back without a development timer, so, start with a plain back and do the following:
Feel free to contact me with any questions or news about your build!