My Mom has an 86 Monte Carlo SS. The caliper is rotated up a little. The bleeder screw is at the highest point. I don't know how else to explain it. I can't get a picture because I'm 500 miles away. I'm willing to bet all GM A-bodies had the same caliper though. You'll find that the Monte Carlo's brake hoses are nice and short too (and cheap) with an anti-kink sleeve.
Most of the aftermarket kits put the caliper up high to "protect it." The problem with this is that the higher they go the more potential of tearing off a brake hose because the hose actually starts getting into a bad spot. Where are your front calipers? Does it really matter where your rear caliper is as long as it doesn't hang below the axle tube? Probably not. Besides, unless you run some outlandish wheels the caliper should be protected by the rim and tire.
Any of the 80s calipers will work that take the #52 pad. Trucks, vans, cars, et cetera all work. They come in different orientations, different bleeder positions, different banjo bolt directions, et cetera. They even come with different piston sizes.
If you want to be really goofy you can swap caliper sides and have them on the front of the axle. Kind of retarded in my opinion but people do it.
Anyway, I went to rear discs so I didn't have to pull my drums to hose out the brakes. Every time I came home after playing I'd have to hose out the mud, sticks, grass, and stones. The main reason was so if I broke a C-clip I wouldn't have my tire going AWOL.