I hate to start throwing money at my next best guess. Could be drums, rotors, or drive shaft? Looking for answers.
Call around to any local tire shops that have been in business for a long time; ask if they can balance the tires on the car. It used to be a fairly common option, but it seems that most newer shops don't invest in the equipment to do it.
I actually bought the equipment to do it myself, but haven't found the time to apply it yet (need to get the garage cleared out first).
You can also try to spin them up yourself and at least get an idea of where the problem is. Put the car up on jackstands (making sure they are secure) then slowly run it up to 50. Being off the ground will exaggerate the shake, so only go fast enough to detect the problem. You probably don't want the car jumping off the stands!
For the rotors, what I did was to clean the grease out of the bearings, then reassemble the hub without grease or the seal and set the clearance as tight as possible without causing any drag. Then turn the hub, stopping every 1/8 turn or so (45 degrees) to let go and see if it wants to turn from gravity. If it will turn itself, it has a heavy spot. After I got that to pass, I tried spinning mine up using a cup wire wheel in the angle grinder against the edge of the brake rotor. I used a spare spindle clamped in the bench vise, but there isn't any reason you couldn't do this on the car (on jackstands).
For driveshaft vibration, one of my books recommends using a large worm-drive hose clamp to add some weight to the shaft. Just tighten the band around the shaft, the worm is what provides the weight. Try it at each end, in 3 or 4 positions around the shaft. If the shaft started out balanced, then each position of the clamp will be equally out of balance. But if you find a "sweet spot", the shaft was out of balance and you can start trying various positions near the sweet spot to get the best one. Multiple clamps can be used if you need more weight.
Or just take it out and have a shop balance it for you. They will also be able to detect if a U-joint was installed wrong or the shaft is bent, etc.