The router feeds a Sonicwall firewall. The Sonicwall does the mapping of multiple WAN addresses to internal servers.Are you trying to have the RV345 feed a Sonicwall? If the answer to that is yes, then that's a waste of hardware. You could just have the Sonicwall and be done with it.
I do understand the the RV345 could do this but we are trying to mirror an old vendor supplied system with a Cisco 1841 feeding the Sonicwall and the old system did this forwarding just fine.
That is normal (I have a Cisco RV325). The outside WAN is for your external IP and the inside WAN is a non-routable IP range like 192.168.x.x