Hi there!
Welcome to the forum! I hope you will like it
As far as I know, the drive shafts are identical. As your drive shafts are new, they probably came from different original manufactures before they were remanufactured - thus the different dimensions. A weight difference shouldn't be able to give you severe symptoms at low speed like the one you describe, which sounds more like crushed CV joints to me?
I think you should take them off again and recheck everything. There may be something that hasn't been fitted quite right.
Doing gearbox removal in 15 minutes is very well done!
- Anders