vibration in 96 GT

I purchased a used 96 GT in December, and have been doing a little work on it to get it back into pristeen condition. Just put new Fulda 245 ZR50 16's on it all the way around, had the front end aligned, replaced the glass packs with Flowmasters, and had the windows tinted. I've noticed since I bought it that there is a vibration that seems to be coming from the drivetrain that is more noticeable when I am accellerating. It seems to smooth out when I let off the gas. I hear a whine in the rear of the car, not sure if it is gears, wheel bearings, or U-Joint. Have not had a chance to really check that out yet. Just looking under the car, the driveshaft looks like it is really rusty. Some of you might remember that the clank I heard in the rear a month or so ago was upper control arms being lose from the rear axle. That has been fixed with new control arms and bushings. Like I said, don't know if the whine is possibly a U-Joint, rear gears or rear axle bearing (wheel bearing). I know the angle on the rear u-joint was really off when the upper control arms were loose. Any ideas here or help would be appreciated....Not rich, gotta try to figure it out myself and save that outrageous shop fee if you know what I mean.

the problem youre describing could be the driveshaft. I just picked up a 95 Cobra a little while ago, with a pro 5.0 shifter and some mods. at about 80mph or so i start to feel a vibration that feels like the car is going to shake apart if i push it to far. The guy at my shop suggested an aluminum driveshaft. he says the stock steels ones are not balanced all that well, they get worse with age and power mods, and that the aluminum route should fix it up completely. he has done alot of work for my other friends on late model stangs, he knows his stuff. the driveshafts are about $170-180 and the shop charge should be below $50. it tkes all of ten minutes to do, including pulling the car in and out of the garage. :iceslolan