Just read the artical in Rod & Custom twice and still don't see how you can do this when most cars are 4 inches off the ground = angle of a drive line at ride hight. Do you put the car on jack stands with the frame level ? Do you measure all 4 corners of the car & raise it up the same amount ? Do you raise it with a 0 angle on the carb-intake ? Need set up instructions. Have a vibration wheI let up on the gas.
Might want to check some of the driveline websites. There alot of disagreement about the angles. Most of the time I've dealt with it, the rear angle was too high.
Lots of different ways to check it depending on the tools available. Best way is to set the car on those drive on ramps (matched set of 4). then the suspension height and frame angle are correct for how the car is driven. Make sure all 4 tires fit the ramps. You don't really want to be setting it after everything is built, though... That should be done as the suspension is going in, or is that what you meant?
If you put jackstands at all four corners of the suspension then the car will set at ride height. They have to be under the suspension so it acts just like its setting on the ground then you can measure drive shaft angles. There should be no more than +/- 1* from front to rear. to do this turn the drive shaft so that one yoke is pointing straight down, then take a measurement with an angle finder. Then rotate the shaft 90* and measure that angle, subtract the smaller from the larger that is the operating angle of the first u-joint. Then do the same on the other one, the numbers shouldn't be off more than +/- 1*. Usually a driveshaft vibration due to improper operating angles will get worse with speed (35mph or slower), not when you let off. Balance issues become noticeable above 35 mph and will never go away like a tire imbalance. You might want to check the tailshaft bushing on the trans. The pinion should be pointing down 2-3* BTW at rest.
You can take measurements with the vehicle in the air as long as the weight is supported by the suspension not the frame. Jackstands under the rear axle and ramps or blocks under the front tires, the frame does not have to be level. Pull the driveshaft and measure the front angle on the end of the trans output shaft. Measure the rear angle at the yoke on the differential. Ideally the angles should be close but optimum angle can vary depending on the suspension. My GTX is set 3 degrees nose down because the pinion will try to climb up the ring gear when power is applied, even with Super Stock springs and a pinion snubber. The '58 is a cruiser so it's at 1-2 degrees nose down. Both are issue free although it took half a summer to get the GTX fully sorted out. http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php
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