Key Differences between 8000 and 8500 Input Units

[affordablelaser]

I used to rebiuld the 5SI an 8000 input units, but now am up against an hp CLJ8500 input unit.

Speaking to technician who are very familiar with the two; What are the differeces between the models? And is it possible to change one into the other given the needed parts (ex. motor, pcb, metal guide, etc.)?? I know many of the parts are the exact same, but how far does that go?

Thanks so much!