Under Virtual IP's are you using Carp, Proxy Arp, or IP? If you want to use 1:1 NAT, go ahead and do so for that specific IP address, then under the firewall rules add in a rule to match the traffic you would like to permit. It should be that simple. Additionally, the IP's 73 and 72 are within your given range correct? Are you using the correct subnet mask?
Curtis
