Yes, but it is tedious and requires tweaking mode lines with trial an error. Incorrect mode lines can damage these old CRT screens. I would caution you NOT to trust mode lines found in xorg.conf files on the net. I did when trying to get the lower resolutions and managed to create a pretty orange glow out the left side of my G3. I decided to learn how to create and tweak mode lines myself. It would take a pretty long post, but I'll try to help if you want to try.
One thing that threw me for a loop until a tip thanks to rsavage over on Ubuntu forums--settings stored in PRAM impact geometry. Adjusting geometry in OSX on these will impact your geometry in Linux.
A safe tool to play with is apt-get install fbset. It is command line and doesn't save settings, but will let you move the screen around a little in small increments.
fbset --move left
EDIT: Also, these are analog CRT's so they will change with age. A perfect mode line today may not be perfect in 5 years.