Does anyone have any recommendations on connecting two layer 3 4506s with two ASAs? We are about to purchase a second 4506 and a second ASA for failover. 4506s will be in layer 3 running EIGRP with l3 etherchannel between them. I'd like to have each 4506 have a connection to an ASA. I'm just trying to grasp how to set this up.
"So GLBP requires layer 2 link between the two"
99% sure about this - need to do a bit of reading. HSRP definitely does and i can't see why GLBP wouldn't unless you have read differently somewhere.
Nothing wrong with L3 from access-layer as long as you don't need to have a vlan across multiple access-layer switches.
Yes you wouldn't need the direct failover cable between the ASA devices as you would be running it over the L2 link between the 4500 switches.