Left Cover. The cover on the left is a later model 748/916/996 cover. Notice the position of the pick up mount hole. It is further to the left of the water pump and the case  actually bulges out to accommodate its position.

Right Cover. The cover on the right is for a '95 916. The position of the pick up mount hole is about a 1/4" further to the right and the case does not have the bulge. The cover also has the RPM pick up hole and air gap inspection plug drilled out. These are located on the upper part of the cover to the right of the water pump. I believe this cover was also used on the 851 and 888.