Stupid question here but I can't really figure it out..

I bought a polished alternator off a user here, and am going to install it, but the main bolt that goes through the water pump - the proper size that threads through the nut on the back side does not fit through the hole on the front side.

I'm 99% sure this is an FD alternator as it was advertised as I when I bought it and it looks identical to my old one.

Am I missing something here?

 

If you saying that the bolt you have is to small then yes I had the same issue with mine. I found out after I bought a new one from the dealer. Just step up one size ( what I did) , you can also switch out the nut but you have to remove the spacer in front of it first.