That serial # is confusing to me... The frame sure looks like either a Manta-Ray or a Fastback 5 speed frame. I'd bet money on that... Thing is though, those bikes weren't around 'till mid or late '60s. That brake bridge on the frame you have is intended for a caliper rear brake, which indicates a 5 speed frame, not a coaster brake model. I seriously doubt they made a 5 speed model in '58. The first Stingrays weren't 'till about '63-'64. Are you sure you're reading the # correctly, or that no one has altered that #? It was REALLY common for those to be stolen & parts switched around in the '70s...