I tried one of these on a 71 Continental. It was too wide. If I centered the axle the front derailler would not push far enough out to get the chain on the large chainring. So I adjusted it to stick out as far to non-drive side as possible and ended up with a working but crappy chain line, and a left pedal that was a 1/2" further out from the BB than the right pedal.

Maybe I bought the wrong size/type, it was designed for a BMX bike.