Koni Classics will give a superior ride, are adjustable, and rebuildable too. I put 88,000 miles on an original rebuilt set of them and they were just as good as were the day I installed them.

Z

 

I have them on my white 66 GT convertible and am very pleased with them. A definitely plus being able to tune the shock to ones liking via a simple flip of a knob. They look good too. TS601 in the back and TS401 in the front. Upgraded rubber to Polyurethane.

 

I have QA1 adjustables on the rear on Jane. They are good for cranking up the rigidity when I need the shocks to help compensate for the heavy loads I put in the back of that car when road tripping.

As far as ride quality though, I don't think they are super spectacular. The superior dampening power of the Bilsteins I've got in the front is very readily noticeable every time I go over a speed bump. Then again, I don't know how much better the Bilsteins would be in the rear of the car, as I've never tried them to find out. I still suspect they would be better.

 

Usually more important than brand is getting them valved to the car/spring you're using. I'm guessing the folks at RCD do that for the shocks that SoT and OT sell. If i remember correctly, they're also a digressive design in the shim stack which also is a good "all around" valving. I haven't used the QA1 but others seem to like them, but I'll put my hat in for the bilsteins.

As far as ride quality though, I don't think they are super spectacular. The superior dampening power of the Bilsteins I've got in the front is very readily noticeable every time I go over a speed bump. Then again, I don't know how much better the Bilsteins would be in the rear of the car, as I've never tried them to find out. I still suspect they would be better.

I haven't driven the mustang in anger with them yet but I've got the bilstein's in the rear as well. From doing some bed-in and driving around they're great. Albeit a different package, I have a similar set of application-valved bilsteins on my rallyX car and absolutely love them. Once you start working them through the stroke they respond very well.

 

I have used QA1's on the street and drag track. Super Pro. Excellent racing shock.
Today I would go with Viking Shocks double adjustable for full race. I think they may be even better at the track.
If your just driving around on the street get some Koni's or Bilstein's for economy. It won't make much difference.

 

I have the Viking double adjustable shocks on the front. I like them. I also like being able to adjust them to my driving style and being able to dial in the ride height. In all honesty they were probably overkill for my daily driver but they were a gift. No regrets.

 

I ended up going with the QA1 single adjustable coil over shocks on the front with 450 lb springs and single adjustable regular shock in the rear. What a difference in the ride! The suspension was just too stiff before with the beefy front coil springs (.600 diameter) and KYB gas shocks. I raised my ride height in the front about 1/2"-1" as well. I like the coil over setup Street or Track has. But that would have been an entire new front end and about $3k. The QA1 coil overs fit in the stock spring location. Because of that, the only real thing I had to take out were my roller perches while keeping my Global West upper control arms.