I was looking to purchase an Air/Fuel gauage to put on my 1989 Chevy Silverado 1500. It has the 305 engine and I was curious as to how I go about installing it. Can i get it to read correctly from idle up through normal cruising speeds? Thanks in advance.

Yep.
I have a PLX wideband O2 in my Burb...which is running a guage in the cab.
You need to have an O2 bung welded into the exhaust (for best..and permanent) results.
You can just plug it into the cig lighter/power outlet to run it.
Here you can see the OEM narrow band bung as well as the extra bung I welded into the exhaust.

http://img.photobucket.com/albums/v35/hquick/4L60e%20to%204L80e/P9290011.jpg