The frame may be a 76 but your rear wheel setup is a 77 xlch (only year and model with that type brake setup). Most likely previous owner pieced together a few basket cases to build a complete bike. Nothing wrong with that. My sporty has 77 lower end, 80 top end, front end came of a panhead and also has a shovelhead part or two. Only problem is the more you customize, the harder it is to get parts when you break down. Also old sportys tend to be a bit temperamental. Get to know your bike inside and out. You will probably have to do your own work on it. Not a lot of mechanics will work on these old classics.