Well check it out. There doesn't seem to be one expert on this (probably because the real experts ditch all the stock shit and throw on a kit). Based on the model, your exhaust will be different. Mine was from 1978, and by then they made it so you couldn't remove the baffle, so I had to drill holes in mine.
Yours' looks different but I can't really tell. All I know is I was having one hell of a time removing that baffle, so if you are too, it doesn't come out, just drill holes.
If you're going to keep running stock, you might consider ordering one of those new sito stock exhausts from 1977. They're the same design, but not restricted. They only cost about $40 or so.