I would like to know if I can config two ASA 5520 as fail over, and at the same time having two ISP as fail over which is connected to the ASA.
u could configure ur firewalls in active/standby mode and connect one ISP to one of them and other ISP to other one
and use the foolowing command to make sure incase of the ISP connected to the ACTIVE ASA failed the asa will failover the other one
Firewall(config)# monitor-interface if_name
however u gonna make one device and one ISP linke passive [waiting the other one to fail]
have a llok at the following link of how to configure ASA with two ISPs links
and the following link of how to configure active standbay in ASA
please, if helpful Rate