ISP link failover from SRX firewall to SRX router

Hi,

Please find below Network topology and suggest suitable option to achieve ISP link failover/traffic diversion on firewall

1) For internet request core switch has default route towards SRX340

2)For MPLS request core switch has static route towards SRX240

3) SRX340 (HA) has default route towards ISP

4) SRX240 (packet mode - Primary and secondary) has VRF configuration to achieve ISP link failover

Here my query is - On SRX340 if ISP link failed internet traffic should routed to SRX240. If i tracert from internet router towards SRX240, first hop is SRX240 ge-0/0/3 interface IP.

We can directly connect one more cable from SRX240 to SRX340 or RPM configuration with next hop ge-0/0/3 interface. My main concern is routing. how packet will be traverse.

Thank you...