Thanks. Then it appears the gusset was welded on to do so.Welcome, it's a swingarm frame that was converted to a hardtail.
It's a '66-'69 Flatside Shovelhead (please don't call it a "panshovel") engine. As already noted, it's a converted swingarm frame. I have a good start on your project, ready for a new owner, $4K, in middle Georgia.