Summit and Jegs sell ring and pinion install kits w/ everything you need. Call them and they'll get you set up. They also have partial kits (no cover gasket, etc..)
That may or may not be correct for your application. You need to match the drivetrain angle (i.e.) centerline of crank shaft through output shaft of transmission. If your drivetrain angle is greater than 4 degrees, I'd suggest you adjust that to get below 4 degrees first.
You want shims that are no more than 2.5" wide, which are pretty much standard. Also cast aluminum seems to bend into the proper arch better than cast steel.
Early model Cougars had wedges in them but it's not likely to be the angle that you're looking for. If you know where one is it might be worth checking out though.