I also have an annoying shimmy and shake as I pass the 40 mph threshhold. Maybe I'm breaking the VW sound barrier. I Feel like the front wheels are going to fly off.
SC, you are experiancing the Stuper Beetle Shimmies. It's an illness all Stupers were born with, but it can be cured . . . well maybe not cured, but it can be put into remission for years at a time. Go to
http://www.toplineparts.com . . . they specialize in lowering Stupers, but they also have the stuff you need to make your Stuper handle like the sports car it is.
The main things to check are:
1. Your wheels. If they are even SLIGHTLY warped, out of round or out of ballance, you will have the shimmies. There is no need to do anything else to the front end until you wheels and tires are right.
2. The control are and sway bar bushings. Replace 'em whether they need it or not . . . trust me, chances are they need replacing! Get Top Line's urethane bushing set.
3. Check the Stut inserts, Steering Dampner, Pitman Arm Bushing, Ball Joints, Steering Gear, the Steering collumn u-joint shaft, anything else connected to the front suspension. Replace anything that is worn.
4. Front end alignment.
5. Find some curves and enjoy your handy work!
The engine does not have enough power to drive in 4 th gear. That is a problem. I'm not sure what to do about that.
Does it run OK? If it's running smooth, but just won't get up to speed, it could be something as simple as slack in the accellerator cable . . . or it could be a timing or carborator issue . . . or it could be low compression.
I'd check the cable first. Pull the breather off, have one of your kids step on the gas pedal (make sure you have the keys first) and see if the trottle plate opens up 90 degrees.
If that's not it, you need to do a compression check and go from there.