Thanks for the responses and the welcome.
After doing a little remeasuring, here is what I have come up with so far:
Heatsinks that I know will fit:
Zerotherm Nirvana 120
Asus Triton 78
Arctic Cooling Freezer Extreme
Xigmatec Cobra D984
Coolermaster Gemini II
Coolermaster Hyper N520
Thermalright Ultima 90
One's that I believe will fit, but can't be 100% certain without trying them.
Tuniq Tower 120
Scythe Ninja 2
Sunbeam Core Contact Freezer
The Asus is out of my price range, but is included for as complete a list as I have found.