Bike has been painted so serial # was hard to read but it looks like a 69.
Looks like somebody stripped a fastback to build this.
Fastback wheels and fenders.
Cool bike with a cool seat.
Fastbacks didn't have cantilever frames. Frame is likely a StingRay or Typhoon or some other model. A fastback cantilever don't look bad though. Turn that front fender around! Gary