ROUGH RIDE..HELP?!?

[todd95GT]

If any of you read my previous posts, you know I just picked up a 1995 GT/5-speed coupe. Here's the problem.
The car rides really rough. It's got 17x9 CObra R's on it with 275's rear/255's front. It doesn't seem to be the type of harshness associated with a low profile tire though. While accelerating, the steering wheel and brake pedal don't shimmy as if it were the brakes or wheel balance. It feels as if the shake is coming from the rear end. It's a very choppy feeling-almost like wheel hop but at a faster rate of vibration. I was thinking it could be the rear bushings, maybe the control arms, because intermittently, I hear a chirping sound, almost like a high-pitched rattle-coming form the rear during normal acceleration and at low rpms. What do you guys think I should look into?