If you follow the positive cable from the battery, it should lead you to a black round piece of equipment that is mounted on your inside passenger fender and probably about 1 or 2 feet from battery. There is two posts on it, the one side comes from your battery and the other side goes to the starter. This is what I call the solenoid. I have never heard of a starter relay but that maybe right on the starter itself. I assumed that you checked the connections already and was still getting the clicking in my previous post. Sorry !!
I have never had any problems with my starter on either the '87 that I had or the '94 now. The '94 was giving me problems after I put the chip in. Turn the key and nothing, go wiggle the positive on the battery and go try again and it would start right up. Bought a new battery, still the same problem. Went and bought a new solenoid, replaced and haven't had a problem since. If memory serves me correctly, I also change the solenoid out of my '87 when I had it. Hope this helps.
Have Fun & Keep on Truckin'