Instead of just putting shims in there check the angle to get it perfect.
Get an angle meter like this
or if you are cheap (or resourceful) you can do this
Measure the angle of the driveshaft tube, and then the angle of the pinion (you can measure that by putting the angle finder on the coverplate surface or the bolt heads if the bolts are the same, just remember its going to ba a 90* difference) and adjust the pinion so the pinion is 1 to 1.5 degreese below the driveshaft.
If you measure the drivesgaft at 16*, and the pinion at 12* a 2* shim will get it to the right spot. Its 4* off, but as you raise the pinion the driveshaft will also raise up decreasing the angle. So 2* higher on the pinion will also move the driveshaft up about 1/2 degree which will leave you with the perfect 1.5* below a straight line.