From the mid-70's on there are three versions of controls for the Evinrudes/Johnsons. You'll only need to worry about the second two:
1) Mid 70's to late 70's ('79 I believe) - Control handle directions and cable travel are compatible through today. In 1979, the cable ends changed style. They still fit, but a clip was removed. Electrical connection is with the Big Round Red Plug, compatible from mid-70's until 1995. In 1996 the plug changed to the small deutsch connectors.
2) 1979 - 1995 - Control handle directions and cable travel compatible through today. Cable ends compatible through today, no clip. Electrical connection is Big Round Red Plug, compatible through 1995. An adapter plug is available to adapt older controls to newer motors. Adapters are expensive.
3) 1996 - Today - Control handle directions and cable travel compatible with older versions. Electrical connection is with small rectangular Deutsch connectors. An adapter is available to connect new controls to old motors. Adapters are even harder to find and expensive.
If you are certain about your model year on the motor, you should be using controls from #2, which means controls from 1980 through 1995 will work fine. Easiest way to determine is to open the engine cover and look at what color the main wiring connector is. If your model year is correct, it should be red.
You should be able to find a set of controls on Ebay for ~$150 or less. Probably even less if you stumble across something on Craigslist. I've seen them sold from $60-$100, but you have to be on the ball to get them for a good price.
Good luck!