Can you modify the machine to accept a Polaroid 550 back, Fuji PA-45 back or Fuji PA-145 back?

The pack films in BW and Color are still being manufactured by Fuji, and are quite excellent.

I suspect a modification to the back will be less expensive than a digital retrofit.

Even better would be to fit a Graflok back to the machine, which would allow you to use Polaroid and Fuji Backs, 4x5 film, roll film and Digital Sensors.