Vibration and Noise Issue

So I just finished swapping in my new 8 3/4 and have run into some new issues. The first issue I noticed was that the driveline seemed to make a pretty nasty noise around 40 mph or so. It is most evident just cruising around town in 4th, but if I wind it high in 3rd you can start to hear it as well. It sounds kind of like cast metal scraping. I initially thought it might be the brake drums skimming the backing plates (the brakes were pulled from a different housing), but when I jacked the car up and let it run with the wheels off the ground it doesn't really sound like it's coming from the wheels and it's mostly speed based. The second problem is the car has a horrible vibration to it at highway speeds, like vibrating chair bad. I took a look at the driveshaft while it was running and it doesn't look like it's turning around center, however, it was the same driveshaft that was on the car before with the old rear end and it never shook like that before and I put brand new U joints in it a few weeks ago. My dad and I were guessing that maybe it's a pinion issue, but does anyone else have any ideas what it might be more specifically? The car also just got brand new wheels and tires with the axle swap, so everything should be all balanced up.