Also there could possibly be a sticker still underneath the seat pan. If it's still there, it would indicate 1972. 1973 and up would have a serial number stamped in the side of the seat pan on the torque converter side between the 3 and 4 ( left to right) seat pan snaps.
It is probably a 1972 and up due to the style of the rear sprocket. They only offered a Roadster 2 in 1972 and up with the 12" wheels. Do you have a shot of the recoil side? That can tell younif it's a 1972 or 1973-75. Also does the engine have a plug in the front for lights?