Do you want to use the printer function,too?
Does the scanner part of your Lexmark work through your Image Capture app?
Some scanners will work natively (no separate drivers needed) through Image Capture.
The installer app for that certainly is not a universal one. But, the printer/scanner driver itself might not be PPC only.
Maybe you could try the Lexmark on a Mac the WILL allow the installer to run.
If you have access to a Mac running 10.6, or older - You could install the scanner/printer on that system, then move the relevant Lexmark files to the corresponding folders on your own Mac.
The software should mostly be in the /Library/Image Capture folder, and the /Library/Printers folder.
I don't know for sure it that will work, but if you do an older Mac, you could try it.