Commodore PC 20-II is almost exactly the same as Commodore PC 10-II, but it is equipped with 20MB hard drive. My machine is unfortunately missing the HDD and the controller. It should be possible to connect MFM drive and controller, as described on the PC 10-II page.
It is the same motherboard as in PC 10-II. Please refer to that page for dip switch settings.
RAM Extension Module
The original power supply was missing in my machine and I managed to get a replacement from Commodore PC 10/20-III machine (according to this document). The replacement power supply is Elec & Eltec 307506-EA. It needed new mounting holes to be drilled, but otherwise fits perfectly. Pinout is described on PC 10-II page.
PC-II was shipped with ATI CW16800-A, it is described in details on PC 10-II page.
Floppy Disk Drives
360KB ALPS DFC222A05A, jumper settings are described on PC 10-II page.