I'm assuming this will be for an outdoor setup
There is a nice calculator here for looking at point to point links, http://www.proxim.com/products/knowledge-center/calculations/calculations-system-operating-margin-som
You should aim for a operating margin of 20 or more. Using an AP-ANT-93 and taking the receive sensitivity values from the AP135 datasheet you should get out to 360m with 5GHz-HT20-MCS7/15/23, and EIRP (antenna gain + transmit power) of 20 dBm.
Using 5GHz-HT40-MCS7/15/23 it only works out at 240 meters.
There are other things to consider such as line of sight and other environmental factors, but that should give you a start.