2000 s10 extreme vibrations

i have an s10 that came with a vibration at highway speeds was told i needed to replace the drvieshaft so i took it to a place that just does driveshafts was told i only needed the rear piece that he had a conversion to a single u joint that works well after install the vibration at highway speeds is gone now i have a vibration from 0 to 20 much harder than original one was told too shim the rear 2 degrees thats been done vib still there any ideas where to go

i have an s10 that came with a vibration at highway speeds was told i needed to replace the drvieshaft so i took it to a place that just does driveshafts was told i only needed the rear piece that he had a conversion to a single u joint that works well after install the vibration at highway speeds is gone now i have a vibration from 0 to 20 much harder than original one was told too shim the rear 2 degrees thats been done vib still there any ideas where to go

Has it been lowered or raised?
Jack it up and put stands under axel.
Start engine put in gear and speed up slow from 0 up to bad shake.
Then remove tires and wheels and bolt on drums /rotors and speed up again and see it still shakes.

Was drive shaft timed up? with U joints timed?
Was it balanced when done?