If you double the stack size as suggested by @dicko in Maximum PBX stack exceeded - #11 by dicko you can have 120 routes. However, I get the feeling that the system still won’t meet your needs.
60 trunks??? What’s your business? If you are reselling termination (with enough volume to make a living at it), FreePBX is woefully underpowered for the task. Take a look at Kamailio SIP Server as suggested by @cynjut .
If you have e.g. an import-export business dealing with many countries, IMO you don’t need more than 5 to 10 carriers and should probably use an aggregator where a tech prefix can select the carrier. For example, see http://www.anveodirect.com/ or http://www.telecomsxchange.com/ .
If you have a real need for many carriers but traffic is low, e.g. you’re in the testing or monitoring business, describe the application and we can probably suggest a better method of route selection.