Finally think I solved my vibration issue

Tested with front wheels sitting on old wheels and rear on jack stands. wheels off, drums off, axles out, differenet 3rd members. new transmission mount, new tailshaft bushing. took belts off, factory balancer, swapped motor mounts. The only way i've gotten the vibration to go away is running it with a piece of wood on top of the jack lifting the trans up off the mount. [Qoute]

So reading this here, you have the vibration sitting in the garage I assume because the axles were out. That is what I meant by sitting still, in other words not rolling down the road. If you had the axles out, I would pull the driveshaft next and run it up, maybe with a yoke in the end of the trans to keep the fluid in. If the vibration is still there, it is in the Engine/trans. If not, Driveshaft/ U joints or combination of both. Or something very loose in differential (third member).