Here is another great angle measuring tool.
Its small enough that it may fit above a Z drive shaft, and even better, because of its small size and square box shape, you can put it on the bottom of the shaft. There seem to be many varieties of this gauge available now.
Because the car is likely not parked on a level surface,or when up on jack stands or a hoist. The angles you read may not be actual drive shaft/Trans or Dshaft/Diff angles.
Measure the engine/trans angle by measuring the angle at the valve cover. Then measure the driveshaft angle and subtract the two. keep up/downhill straight.
The diff is more problematic. No flat top or bottom to use as a reference. Have to take the drive shaft off and and measure the flange face angle, then subtract 90.
Use the same dshaft angle minus diff angle thing to get that angle.
The trick is to get them both (trans/shaft and shaft/diff) the same, and both between 1 and 3 degrees. You need some angle to make the u-joint move all the bearings and stay lubed, but not more than 3 deg to minimize vibration.
Also the trans centerline and diff center lines must be parallel. This is pretty hard wired if you're using the stock mounts, but worn engine and or trans mounts will contribute their own error.