There are 2 styles of bb frame bracket: 67-68 and 69. The 67-68 bracket is designed to use the non-interlock motor mount, 69 uses the interlock motor mount. The non-interlock mount is wider and thinner than the interlock mount, thus the 69 frame brackets are shorter and narrower than 67-68. The non-interlock mount unfortunately fits the 69 brackets. It will be a sloppy fit and the motor will be too low.
Confusing the issue, some replacement 67-8 mounts now have the interlock feature.
If the motor mounts are about 3/8" wider than the brackets they are incorrect. The correct mount is a tight fit on the bracket. If not I would bet you have one sb frame bracket. I presume you have a bb trans crossmember.