Try turning the wheel to the point where everything shuts down. Then hold the wheel at that position and see if it will start (turn over) or if the headlights or radio work.
Most likely you have a chaffed or loose wire in the column that will need to be repaired or replaced. Only you can say if that is beyond your abilities or not, but do you know how to remove your steering wheel? I don't. I have removed the steering wheels from classics (65-68s), and done the same on my 2005 with airbag. but I don't know how to tell you to do it on an 87. There's another forum on Stangnet for Fox body Mustangs (79-93), I am 100% sure folks there will be of more help than most of the guys who hang out here.