Yes they almost all had the pivot hole, but not all. Some early SBC engines used a bellhousing pivot ball, and so the block had no boss or hole. I ran into one back in the early 70's when looking for a replacement 283 for my '67 Chevelle. I think the numbers put the donor engine as a '61 or '62 and I had to make up a bracket to bolt to the bellhousing bolts, and situate the pivot ball to line up with my Z bar.
Some early engines also didn't have the rear of the crankshaft bored for a pilot bushing also! That can really screw up a engine swap, and not a cheap fix!