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

I’m curious to see what happens after Robin has his tires balanced. Something I haven’t mentioned and I don’t believe it’s been mentioned, is the high gear clutch can be also slipping causing the vibration. I experienced that years ago in my dads roadrunner. It’ll really show on a 1/4 mile over 1/8 mile. But just add that to the list of possibilities Robin lol.