Lexhttp://www.monitortests.com/forum/Thread-Custom-Resolution-Utility-CRU
I used this tool to run my old LG monitor at 70Hz@1080p without artifacts. Some monitors will allow more, some less.
AT YOUR OWN RISK, find the highest stable value and see how it works. The difference between 60Hz and 70Hz isn't huge, but it's noticeable.
I used my old Acer monitor at 1680x1050 @ 86hz, was amazing till I got a 144hz monitor. Did notice how much hotter the monitor operated, surprised it STILL lasts. ~2 years.
also refer to your monitor's manual. Many monitors can run 1440x900@75hz.