Red at CycleOne Manufacturing made a nice frame for a 360.
In the late 70s, the original Iron Horse magazine featured a designger named Paladin. He had a pretty detailed drawing of a Triumph 500 or 650 with a home built hardtail using the stock swingarm. I didn't have a Triumph so I copied the design using a Honda CL350. Basically I extended the swingarm 2". I cut away the rear section of the frame and welded tubing between the shock mounts on the swingarm and the frame (approximately at the point where the rear of the tank mounted. I also added louvered sheet metal panels between the swingarm and the top of the hardtail which hid my electrics and provided some visual interest to the bike. It turned out very well, was fun to ride and fairly cheap to build.