If it has the original hydraulic system, then those cables connected to the hydraulic cylinders to sense when they were up, down, and to also adjust the depth stop collar. There should be one or two levers coming out of the top of the hydraulic unit to work the remotes. The system will still work without the electric portion hooked up, you just won't be able to control a hydra-lectric cylinder with it. 

If you don't have the levers that come out of the top of the unit, then the tractor has an older hydra-lectric unit. On those, the switches were mounted on the steering column.

A Super 77 should have come with what was known as the Series III hydra-lectric unit. I don't think that anybody is making reproduction harnesses or switches for them at this time. Check with <!-- w --><a class="postlink" href="http://www.korvesoliver.com">www.korvesoliver.com</a><!-- w --> to see what they have. Give them a call, they are very helpful and might be able to find something for you.