Are these the same even though the front nut is not there in the original but is located somewhere else?

 

It will. What you had on your car is the original. The 2 right pics is the upgraded version for the belt tensioner. Easy to R/R. Change your belt as well. Where did you buy it? Go to Benzworld.org and search belt tensioner. It been discussed there a lot.

 

fdte320 is correct, that is the updated part, but function is exactly the same.