Accessing remote WAN-1 modem of Balance-1 from another Balance-1 via VPN tunnel

Two LANs both have Balance-1 for routers.
Both LANS have modems with same unchangeable IP address on their respective WAN-1 ports.
Both LANs are connected together via a Pep VPN tunnel.

Would like to be able to access remote LAN’s modem from local LAN over VPN tunnel. However, since modem on each LAN has same unchangeable IP address, entering that IP address naturally results in being connected to Local LAN’s modem.

Is there a way to setup a unique IP address (or port) on local LAN that will get routed to remote LAN’s modem on WAN-1?

Look like both modems at each side is having same IP address (e.g. both are

There is no way to route the identical IP addresses in Layer 3 environment. Please change the modem IP on either side. You may get help from ISP if needed.

Not possible. The IP address of both modems is hard set via Firmware. There are no options to change either.

If changing modem IP is not possible, then there is no normal way to access an identical remote network from local. You may put a RDP PC at remote side then access the remote modem via the RDP session.

Hope this help.