Aaaaaaaa, have you tried another DOS?

I have my Ghost 2003 and Ghost 8.3 both set up on boot disks using Windows ME Dos.
I've not seen any gigabyte limits so far.
I'd think that PCDos is just TOO old to do what you need it to do.

Ghost 8.3 is too big to set up on a 1.44mb floppy disk, but you can make a Flash Drive bootable and then add the Ghost files and anything else you like.  Once that's done and working, you can even use a program like Nero to put the image of that flash drive on a CD
making a boot CD with Ghost on it.

I've done all of the above with NO problems what-so-ever.

There are many places on the internet where you can download an ME Boot Disk builder.

Good Luck,
The Shadow