Hi,
Usually, you get the same DOS driver for a range of network cards. DOS drivers are not granualer as Windows drivers.
For Intel 82566, you have the same dos driver used for intel pro/1000 (e1000.dos). Probably, the existing intel pro1000 driver would work.
When you select Add driver from Ghost Boot Wizard, it allows you to select the folder and install the driver. However, this may not work depending on the folder/file structure provided by the network vendor.
Alternatively, you can use the universal packet driver (UNDI) which is common for all PXE supported network drivers. Intel cards are working pretty well with UNDI driver.
Hope this helps.
Krish