She has been on 3 alignment racks in 3 different shops and although a little better the vibrations are ever present. The pinion angle is correct according to 2 places and my gauge at home. The first place couldn't check it. The last shop found the thrust angle off and brought it back to spec which definitely helped some but the pinion still hops when above 45mph. Just a little less violently now. They blamed the wheels and needing hub centric rings but it does it on jack stands without the wheels mounted.
I can feel a little play at the tailshaft bushing so I am pursuing a rebuild or replacement transmission. I don't think it will change the vibration but don't know what else to do. I don't see how a bad trans can cause the pinion to hop unless the bushing was destroyed.
The only other thing I am wondering is door gaps. Both my current cars have narrow gaps on passenger door vs drivers side door. The t top car has no gap at b pillar. The paint has rubbed off near the latch it's so close. I previously found the left tie rod end bent. Maybe the whole car is bent causing the rear axle and engine to be out of line side to side vs up and down. Them adjusting the thrust angle made a bigger change then anything else I have done.
Had it at a frame shop this week. Doghouse is out of square 1/8" or so. That should not cause drivetrain alignment issues. I have that much adjustment in the mounts and shoving the trans and/or engine left and right doesn't really change the vibrations after the thrust angle was adjusted.
I did notice when running it to different body shops that the vibration gets more pronounced the longer the drive. This implies it's something heating up. Could be the u joints being stressed but I've ruled out pretty much everything except the used T5 at this point.
I have one more shop going to go over my work this week. They will triple check pinion and drivetrain angles. They do this type of work and actually seem interested in my problem. The alignment/suspension shops I had it at did their part but I don't think either were actually interested in dealing with the vibration. Reading others just needed shims I don't want to spend a couple grand for a new trans and find out it was $100 worth of shims coupled with not being able to use an angle finder.
Received a crazy estimate to paint it from the body shop. In my mind I have already completed half the job. Would love to have a fresh coat of...... maybe a Kona Blue. For what he quoted I can learn to paint and then restore the rusty Cobra as well.
I find a lot of body shops quote based on "what they can get" vs "based on cost of the job and a mark up". This inflates the price and makes prices sometimes unreasonable.
If the body shop is at all good, this only means they are busier, and with an abundance of work they don't have to be pricing fairly.
They do this for a number of other reasons, least of which is to cover costs from botched jobs, re-do's and mis-quotes.
Or there's the scenario that they don't want that kind of work so they price the job pretty high with the expectation the customer won't go through with it with them. Kinda goes along with what @429MII says about pricing if they're busier.