The MB U-joint is kind of unique in that it is a single unit. A "normal" driveshaft has one at each end that work in concert to minimize stress on the joint due to shaft angle.
I'd suggest considering redoing your driveshaft to put a U-joint on either end. My friend Druk had this issue on his 606->107 swap. Here's a post detailing his solution -
http://www.peachparts.com/shopforum/3279492-post74.html
Or alternately incorporate CV joints which would make for a smoother transmission of torque.
Just a thought....