If I put them back in I'll definitely go with new. Having another look at the crossmembers of the two vehicles it looks like the one on the driver side will just bolt up. However the one on the passenger side will either need:

1. Be left off
2. A bracket fabricated

Perhaps there is a motor mount for the passenger side where the shock is located behind the mount as on the driver side. Looks like there is a hole on the cross member to mount the shock were it on the rear of the mount.

300D passenger side cross member where shock was mounted to forward side of cross member:


240D passenger side where forward mount for shock is non existent: