The black box is a PCM
PCM - Powertrain control module
ECM - Engine control module
The blackbox wasn't used until 96. with the vortec motors. They stopped using it in 1999 or 2000 depending on the model I think. Before the blackbox the motors were all TBI instead of Multiport injection.
Depending on the tranny you had you would have one or the other,and considering yours is a V6 it would be an ECM, so you probably don't have the 4l80. (just noticed the post that said you had a 5 speed, so obviously don't have a 4l80) The reality is that it doesn't really matter unless you are changing one out. If you have a computer controlled tranny then it would be a PCM. In 1991 the 4l80 was used and it required a PCM, but I believe 94 half ton would only have an ECM.
You probably have the 1227747 ECM. Here are some details about your ECM
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42