1964 Valiant Drive Shaft Suggestion

All

I've a got a vibration in the rear of the car when I get above 60 MPH. I would like to R&R the drive shaft as I believe the drivie shaft is out of balance. I'm looking for suggestion on where to get a replacement. The other reason I want to repalce it is it has two differant size univeral cap sizes. I had to buy four u-joints to put together a two u-jonit that would fit.

Thanks
Bear