Ok. Found some info that suggests the 2400bps RF receiver from SparkFun can be re-tuned to 310. If you look closely at the images, you can see that the receiver has a tuning slug on the back of the board. Check out this article for more info: http://gobighometheatre.com/boblight/.
I guess you should use a scope to do this. But you could try tuning it manually, by using one of your remotes to signal while adjusting the tuning slug until you get a reliable input, using the Arduino as a monitor. When you get a input you would move the transmitter and receiver further apart and start over until you've got reliable input at the maximum range.