Most CRT monitors are relatively forgiving when it comes to vertical refresh, it's the horizontal rate that tends to be the most critical. Make sure the pinout is correct through the adapters and actually routing the signals to the right pins. Still it may not be close enough. The monitor is not junk, it's just better suited to someone who only wants to run it on a Mac.

Multisync PC monitors that will sync to most of the Mac resolutions are still common, so you shouldn't have too much trouble finding one. I second the suggestion to find a Sony if you can. A trinitron in good condition and properly tuned still provides a stunning quality picture IMO.