Can anyone please tell me where the "idle set screw" is on a 87 Bronco 302 (5.0)

 

There isn't one. 87 should be fuel injected. There is no idle mixture screw. The IAC controls the airflow through the throttle at idle.

 

I think there is an idle stop screw - my 86 EFI has one, though the uninitiated aren't supposed to mess with it....
If there is one on the 87, it'll be under the plastic "do not tamper" cover above the throttle body. It's just a low end stop for the throttle plate. To be honest, adjusting it too high or low will cause a wierd idle, because the IAC is always trying to fix the idle. It would be permissable to bump the idle up or down a couple hundred rpm. If you're having idle issues, pulling the throttle body off and removing the IAC for a cleaning is a real good idea. A lot of idle problems come from a mucked up idle air passage.