Typically, you would have received most or all of the creature comforts in the truck.
You'd have had power windows/locks, carpet, lots more chrome than a base model truck, brushed aluminum dash trim or something other than black.
Sliding rear window, A/C was typical, headliner, door pockets, sound deadening insulation, cloth seats and all that.
However as with any make, like a Ford XLT, or Dodge Laramie, they could have been ordered with more options or less and still retain a silverado trim package.
The base package, such as the '87 Custom deluxe 4x4 I just picked up, would be much more apt to have a base motor (4.3L), manual windows and locks, rubber floor, full vinyl bench, no AC, solid rear window, steel wheel with hubcaps, no body trim aside from badging, no insulation for sound proofing, base stereo (sometimes if any).
Another interesting note would be that without A/C, you didn't receive any panel vents.