My brother had a 69 Buick Wildcat and the driver's side mount tore in half. Turns out they changed the mounts somewhere mid-year and the reproduction engine mounts the parts store sold did not fit (tried a set from every parts store in town that could get them).

He ended up removing the torn mount and replaced the rubber with steel. Once back together it did not vibrate like some who said it would. This may be because GM cars have a frame and rubber body biscuits?