Richard
Unfortunately no you can't connect 2 ASA devices in active/active or active/standby over a L3 routed connection. The 2 ASA's need L2 adjacency for their failover connection.
There are a number of ways to extend a L2 vlan across a L3 routed network such as L2TPv3 and MPLS Pseudowire but i'm not sure how the link would perform for stateful failover.
Jon
