Rear end help!

[fireman442]

I have a 1969 mach 1 with a 428. When I first got the car I thought it was strange that only one wheel would spin so I thought it didnt have a posi rear end. On a wet day about 1 week ago I got on it and both wheels took off spinning. Well I decided to try it out this weekend on some dry pavment. Well once again only one wheel spun. Now my new problem whenever I turn a corner it sounds like I have gravel in the rear end so I think that some gears in there are trashed. I am going to rebuild the rear end on the car now but have limited experience on what I should buy for it or where I should get the parts I need. I am in the midwest and am limited as far as salvage yards go. Where is a good source to locate parts I need and since I am gonna have it apart anyway what should I do to it!