I have a 67 500 L and I have swapped the original engine for a rebuilt unit from a 126, including the proper drive shaft switch.

I know a great deal has been written on this forum about the swap so I'll begin by asking for patience. All the posts were extremely helpful in the swap. However, I now have an issue.

When accelerating from a stop, there is a horrible vibration. I also notice that it seems the engine mount sits on the stop (is the spring not strong enough?) I've replaced mounts and springs. Any suggestions of what could be causing the vibration? In case it makes a difference, I have installed sport springs that lowers the car a bit.

In advance, thank you.