Is it a '78? That's what I'd guess from the wheels. I did notice the muffler missing and figured it was in the midst of a resto.
Mine was a '78 but it had the seven spoke wheels. It was a total mess for $2000 but I was too young to know any better. Had '79 Sporster chrome siamese pipes, no rear sets, a blue windscreen on the fairing, and had been creatively wired at some point. Honestly, as great looking as it was, I was glad to get what I had plus a couple hundred back out of it. I'd love to have another, in good shape, one day but the prices have gone crazy on the good ones. Still love the Black Rain bike as a slightly different animal but there's no substitute for the original.