welcome Newb geb78. You say the engine is original? HAcode? How could it be anything but an SS? Of course, the first thing that will be asked on this site (so, I will go ahead and ask) is to provide pictures of the Trim Tag and engine stamps/castings/dates/all partial VINs. Hopefully, you have studied all the related information on the site already and can conclude on your own what you have since there is so much information that is presented so well by our site administrators and founders with more detail topics(and sarcasm/humor) provided by our knowledgable members, here, in the forum. Agree, your pic is hard to determine the "plate". It looks more to be an outline of where a rear ex. hanger was located, but the holes are way too big, so more pics needed, maybe cleaning off that area.
Beat me to it..