The C20 is a 3/4 ton truck, right? If so, you will be a little more limited in your choice of lowering parts and wheels. The suspension is a little different, and the wheels will have more lugs than a 1/2 ton. AFAIK the parts are available, but you might have to pay a little more, and you probably won't have the selection you would if you had a half ton truck.
The other thing to consider is that, assuming it is a 3/4 ton, your truck is a long bed. A lot of people don't like the look of a lowered long bed. Before you make plans to lower it, look at some pics of lowered longbeds and make sure that YOU like the way they look. If you like it, go for it.
If I was looking for a pickup to lower, I would look for a short wheelbase (SWB) 1/2 ton stepside or fleetside. It will be cheaper to lower, easier to find advice on (what product combinations to use to get the look you want, etc.) and look better than a long wheelbase 3/4 ton.
Looks are subjective, though, and your tastes may be different than mine. Some folks might even argue that I have no taste in vehicles, so take my opinions with a grain of salt.
Whatever your choice, ANY nicely done 73-87 is cool!
Slonaker