Hi, thanks everyone for the feedback. They are the Hellwig EZ550 ones. I printed the install instructions and gave it to them.
I had planned on doing it myself but I don't have a jack tall enough to fully extend the leafs which is what the directions call for (and using the jack under the seat takes forever). So I figured while they had it on the lift they could bolt it on since it takes < 5min
Anyway, I was just out again driving it and it definitely seems like the vibration is related to the driveline. I have no other suspension mods, it's completely stock other than the helper springs.
I can feel the vibration when letting off the clutch going into second. It's definitely from the rear and maybe it's just my imagination but I think I feel it through the clutch pedal as well.
So researching a bit more I found these pics in the first post
Is that how they should be??
Overall the ride is definitely improved though. No more bottoming out going over big bumps. I might loosen it slightly, I'll have to see how it feels loaded full of gear.