Hi ukdesignated,
You can do a nat translation where the port does not get translated and only the IP gets, or if you don't even want to perform natting, then use NONAT feature and traffic will be passed as it is.
https://supportforums.cisco.com/document/132066/asa-nat-83-nat-operation-and-configuration-format-cli#RULETYPES
HTH,
Ab
Regards,
Abhishek Purohit
CCIE-S- 35269