High Speed vibration, can't find what's causing it.

In the last month or so I started to notice the race car vibrating when I get above about 90 mph on a pass. Does it only while the car is still accelerating. When I let off it goes away.
It crosses the finish line 107-108 mph
No vibration during burnout or until 3rd gear (727)
So far I have:
Checked u joints and trans mount, also trans output shaft doesn't seem to have any side to side play.
checked motor plate
New front tires (was vibrating before the new tires)
front end alignment ( Stock front suspension. I do need tubular upper control arms as alignment is at its limit, but all ball and other joints are fine)
I would think that warped front rotors would show up before 90mph so I haven't looked at those
Suggestions??
My Van would vibrate or shake over 90. I took it as the wind getting under it and just let it go. Possible you need to drop your front end a little. Other comments are also valued here, I'm just giving you a possible easy way out.