Splicing 1978 connector to 1986 controls

[deerhuntre]

OK, so I've got the service manual and the wiring diagrams but I'm totally lost!! I see all sorts of wires labeled by color and numbered to the plugs, but what do I do with this? Am I supposed to trace each wire in the old and new to its respective component, then use that info to decide what to splice where?

Here's Serial Number info:

Control in the boat and Leg/lower unit from 1986 S/N is: OA907915 (Model 1115726)

Powerhead and wiring for the 1978 on the motor: S/N 5051145 (Model 1115528)