Drivetrain Vibration

The driveshaft has been new balanced.
It was balanced years ago without the slip yoke and that caused a lot of vibrations.
After balancing I was able to drive 90 mph smooth af.
But now my tranny started leaking more and more..
And the vibrations got worse.

I don't want to rebuild it anymore..
So I have to go with a new one.

Any suggestions? Want to stay with 904. Was thinking about TCI Streetfighter..

Thanks to all of you :)