:welcome: aboard Charles!
On the control cable lengths, measuring yours from the controls to the motor is about the only way to do it or by removing yours first and laying them out. Your 1981 Rude is right there at about the cusp where they changed from old to new style cable ends too so make sure yours are the same as the ones your ordering. I'm assuming your obtaining the motors original controls too and not trying to use the one from 1972 because it would be for sure the old style ends and you can't have one of each on either end.
Not sure what you mean about the steering hitting the side of the boat so you'll need to post some pics of what you're talking about there. Steering cables are very precise for length, too short and you're screwed, too long and the cables won't bend enough to take up the slack. What helm to you have, rotary or rack & pinion?