Controls are specific to engine brand. Some controls can be configured for Merc and Johnnyrude, Yammie etc. These are usually made by third parties.
Steering systems are usually universal. Fuel systems are easily adapted.
Wiring diagrams are hard to find for specific models. You can try the Viking website, if they have one. Most OEMs follow the standard wiring colors associated with boat wiring diagrams. That can help, but I recommend tracing each wire you are unsure about.